MCAT Chemistry
what is the formula for formal charge?
# valence electrons- # of bonds- # non bonding electrons
what is wrong with the phrase: i add ice to my glass of water to cool the water?
'coldness' cannot spread. Heat energy is transferred from something with more energy (on average, the warmer thing) to something with less energy (on average, the colder thing). so when you add ice to a glass of water, you're actually getting the water to heat up the ice cubes by transferring some of their energy, not the other way around.
what is the ionic charge created by reactions with group 11 atoms?
+1
what is the oxidation state of group 1 elements?
+1
what is the general oxidation state of H? What is the exception?
+1, except when bonded to a metal, like NaH, then it's -1
what is the charge of most transition metal ions?
+2
what is the oxidation state of group 2 elements?
+2
what is the oxidation state of group 15 elements (nitrogen family)?
+3
what is the most oxidized state of carbon?
+4 in CO2
what is the highest oxidation state that a halogen can achieve?
+7, except for fluorine, and only in the presence of highly electronegative elements
what is the oxidation state of H in NaH?
-1
what is the oxidation state of O in H2O2?
-1
what is the oxidation state of fluorine?
-1
what is the oxidation state of group 17 elements (halogens)?
-1
what is the only possible oxidation state of fluorine in compounds?
-1 (it can only make 1 bond)
what is the oxidation state of group 16 elements (oxygen family)?
-2
what is the general oxidation state of O? What is the exception?
-2, except when it is in a peroxide like H2O2, then -1
what is absolute zero in celcius?
-273 C
what is the most reduced state of carbon?
-4 in methane
what is the ending on carboxylic acid salts?
-ate
what is the ending that is added to a ring sugar when you react it with an alcohol to make an aldol? ex. react glucopyranose with methanol, what do you get?
-oside. glucopyranoside
if K=1, what is the value of delta G naught?
0
what is log(1)?
0
what is the delta G for a reaction at equilibrium?
0
what is the oxidation state for atoms in their elemental forms?
0
what is the reduction potential of hydrogen?
0. The hydrogen electrode is used as the zero reference point for all other redox half reaction potentials
what is delta G for a reaction when at equilibrium?
0. there is no work that can be done by a reaction at equilibrium
what is log (2)?
0.3
what is log (3)?
0.48
what is log (4)?
0.6
what is log (5)?
0.7
what is log (6)?
0.78
what is log (7)?
0.85
what is log (8)?
0.9
what is log (9)?
0.95
what is log (10)?
1
at what pressure does water boil at 100 and freeze at 0?
1 atm
what is the conversion between calories and joules?
1 cal= 4.184 J
if you want to fully reduce a carboxylic acid or ester etc to an alcohol, what reagent would you use?
1 equivalent of LiAlH4 (lithium aluminum hydride). sodium borohydride is not strong enough to reduce carboxylic acids of its derivatives
if you want to reduce a carboxylic acid to aldehydes, what reagent would you use?
1 equivalent of LiAlH4, if you use 2 equivalents, the reaction will go all the way to alcohol
what is the bond type in sucrose?
1,2 linkage that is alpha for glucose and beta for fructose
what are the 3 types of reactions of alcohols?
1. (most important) they act as nucleophiles 2. they act as acids 3. protonated alcohols make good leaving groups Note: an alsohol can act as a nucleophile and an acid in the same reaction, first by attacking and then losing their proton or vice versa
list the following molecules in order of nucleophilic reactivity: carboxylic acids, anhydrides, aldehydes, acyl chlorides, ketones, esters and amides
1. acyl chlorides 2. aldehydes 3. ketones 4. anhydrides 5. carboxylic acids 6. esters 7. amides
what are the types of stress that obey Le Chatelier's principle?
1. adding or removing product or reactant 2. changing pressure or volume of the system 3. changing temperature of the system
what are the steps of solution formation?
1. breaking the intermolecular bonds BETWEEN solute molecules 2. breaking the intermolecular bonds BETWEEN solvent molecules 3. formation of intermolecular bonds AMONG solvent and solute molecules The first 2 steps are endothermic (bonds require energy to be broken) and the 3rd is exothermic (forming bonds releases energy)
in what 4 ways do ideal gases differ from real gases?
1. ideal gas molecules have no size (zero molecular volume) 2. ideal gas molecules do not exert ANY repulsive or attractive forces on one another 3. Ideal gas molecules have completely elastic collisions 4. The average kinetic energy of ideal gas molecules is directly proportional to the temperature of the gas Basically this means that in theory, ideal gases use all of their energy to collide with the container and exert pressure, rather than interacting with each other. We assume zero volume so that there is more space for them to interact with the container instead of one another. Elastic collisions allow for no energy to be lost on anything other than collisions with the container
what are the 2 cases in which enantiomers have the same physical and chemical characteristics?
1. interactions with other chiral compounds 2. interactions with polarized light
what are the requirements for a collision to trigger a chemical reaction?
1. the relative kinetic energies of the colliding compounds must be greater than or equal to the activation energy, and 2. the atoms of both molecules must align in the proper way in order to trigger a reaction Both criteria must be met every time a reaction occurs
what are the 2 reasons we conduct titrations?
1. to find out the concentration of an acid or a base by comparing it with the known concentration of the titrant or 2. to find the pKa or pKb and in extension Ka and Kb of an acid or a base
what is the value of the Boltzmann constant?
1.38 x 10^-23 J/K
what is the equation for the average energy in a system according to the equipartition theory?
1/2 kT, where T is the temperature and k is the Boltzmann constant (1.38 x 10^ -23 J/K)
what is the density of mercury?
1000 kg/m^3 or 1 g/ ml
what is the meaning of deci?
10^-1
what is the meaning of pico?
10^-12
what is the value of Kw?
10^-14. this is an equilibrium constant. The value is much less than 1, so it lies very far to the side of reactants (water)
what is the meaning of femto?
10^-15
what is the meaning of centi?
10^-2
what is the meaning of milli?
10^-3
what is the meaning of micro?
10^-6
what is the meaning of nano?
10^-9
what is the meaning of kilo?
10^3
what is the meaning of mega?
10^6
what is the difference between calories and Calories?
1Cal= 1000 cal
how many equivalent of LAH does it take to turn a carboxylic acid into a primary alcohol?
2 (LAH ia a short form for LiAlH4, a very strong reducing agent)
what is the standard molar volume of any gas?
22.4 liters. The fact that there is a standard molar volume means that any gas will have the same volume if they have the same temperature, pressure and number of molecules
what is the maximum number of optically active stereoisomers that a compound can have?
2^n, where n is the number of chiral centers
how fast do oxygen molecules travel at room temperature?
480 ish m/s
how many transition metals react to give +3 charge?
5
what is the SI unit for electric current?
A (ampere)
what is the linkage between the glucose molecules in cellulose?
B 1-4 glucosidic linakges
what is the formula for carbonate?
CO3^2-
what is the formula for hypochlorite?
ClO-
what is the formula for chlorite?
ClO2-
what is the formula for chlorate?
ClO3-
what is the formula for perchlorate?
ClO4-
contrast Cp and Cv
Cp is the constant pressure heat capacity and Cv is constant volume heat capacity. The internal energy of a system can change due to a combination of work and heat. When pressure is held constant, as energy is added, the volume expands and some of the energy leaves the system as PV work and only some energy goes towards raising the temp. In contrast, when volume is held constant (no PV work can be done), more of the energy must go towards heating the substance, so the temperature will change more than in a constant pressure scenario. Cp>CV since it takes more energy to heat the substance if some energy is lost to the PV work of expansion. This is only relevant for gases, since solids and liquids strongly resist changes in their volumes
what are the 5 transition metals that react to give +3 charge?
Cr, Fe, Au, Al and Bi
in an isothermal ideal gas process, what are the values of E, q and w from the thermodynamics equation?
Delta E= q+w. in an isothermal process, there is no change in internal energy so delta E=0 and 0=q+w, meaning that heat transfer must be equal and opposite to work
if you change the pressure in a reaction, according to Le Chatelier's principle, what happens to that reaction?
Determine which side has more moles of gas. If the pressure was increased, the equilibrium shifts towards the side with fewer moles of gas, if the pressure was lowered, the equilibrium will shift towards the side with more gas. Keep in mind this does not apply if pressure is increased by adding a non reactive gas like He. The pressure changes but He does not change the partial pressures of any of the reactants or products, so equilibrium is NOT impacted
describe electron donating groups
EDGs donate electrons and stabilize positive charg. By stabilizing congugate acids, EDGs make a molecule more basic
how do substituents change the basicity of an amine?
EWGs decrease the basicity whereas EDGs increase the basicity
how can the presence of electron withdrawing groups impact an alcohol's reactivity?
EWGs make alcohols more acidic by drawing even more electron density away from the H, increasing its partial positive charge. After deprotonation, EWGs stabilize the resulting negative charge
how are E and G related in galvanic cells?
G=-nFEmax, so gibbs free energy is positive when E mx is negative and vice versa. negative G means a reaction is spontaneous, so positive E also indicates spontaneity, since F and n must always be positive
what is the formula of sulfuric acid?
H2SO4
what is the formula for hydrobromic acid?
HBr
what is the formula for bicarbonate?
HCO3-
what is the formula of hydrochloric acid?
HCl
what is the formula of chloric acid?
HClO3
what is the formula of perchloric acid?
HClO4
what is the formula of hydroiodic aicd?
HI
what are the strong acids you need to remember for the MCAT?
HI, HBr, HCl, HNO3, HClO4, HClO3 AND H2SO4
what is the formula of nitric acid?
HNO3
what is charles' law?
Ideal gas law that says volume is directly proportional to temperature at constant pressure. This means that as you increase the temperature of a gas in a flexible container, the volume will increase proportionally. V/T=constant
what is the lewis theory of acids and bases?
It defines and acid as any substance that accepts a pair of electrons and a base as any substance that donates a pair of electrons. it includes all substances in the bronsted theory as well as molecules that have an incomplete octet around the central atom
what would happen if you were to react a primary alcohol with PCC?
It would oxidize to an aldehyde
what are the units for entropy?
J/K
what is the SI unit for temperature?
K
what is the difference between K and Q in kinetics?
K is the equilibrium constant and can be found by plugging in the concentrations of reactants and products only when the reaction is at equilibrium. K for any reaction can only be changed by changing the temperature. In contrast, Q is the reaction quotient and the equation to find it is the same is for K, except that the reaction is NOT at equilibrium. Q may have any positive value
what is the equation for the average kinetic energy of a single molecule in any fluid?
KE= 3/2 kT (since there are 3 axes of motion and each has an average of 1/2 kT)
what is the equation for Ka?
Ka= ([H3O+][A-])/[HA] products over reactants
what is the equation for Kb?
Kb is a corresponding value to Ka. Kb is the equilibrium constant for the reaction of the conjugate base and water. it is NOT the reverse reaction of Ka. Kb=([OH-][HA])/[A-]
how do you get Kw if you know Ka and Kb?
Kw=(Ka)(Kb), also pKa+pkB=14
what is the equation for Kw?
Kw=[H3O+][OH-] because water is a liquid and it does not participate in the equilibrium reaction
compare CN bonds to CO bonds
N and C have similar electronegativity values so the N will share its electrons with C more readily than O. Therefore the NC bonds will be stronger, less polar and less reactive than CO bonds
what is the formula for ammonium?
NH4+
what is the formula for nitrite?
NO2-
what is the formula for nitrate?
NO3-
what are the strong bases you need to remember for the MCAT?
NaOH, KOH, NH2-, H-, Ca(OH)2, Na2O and CaO
what is the equation of the ideal gas law?
P is pressure it atm, V is volume in litres, T is temperature in kelvin and R is the universal gas constant 0.08206 L atm/ K mol or 8.314 J/K mol
what would you use if you wanted to oxidize a primary alcohol to an aldehyde or a secondary alcohol to a ketone?
PCC. it is a much gentler oxidizing agent than permanganate/ chromate/ dicrhomate so it will stop at the aldehyde/ ketone stage
what is the formula for phosphate?
PO4^3-
what are the 2 types of work that can be done by a chemical system at rest?
PV work ( changing size or shape using the energy from the system ) and non PV work
what is Boyle's law?
PV=constant Pressure and volume of an ideal gas are inversely proportional at constant temperature
what equation relates the ideal gas constant, and the boltzmann constant?
R= Na k, where R is the ideal gas constant, Na is Avogadro's number and k is the Boltzmann constant
compare when you would use Raoult's and Henry's laws
Raoult's and Henry's laws dont play nicely with each other. Raoult's is most accurate when it is applied to the vapor pressure of a solvent in high concentration. When solvent concentration is high, most solvent particles are surrounded by other solvent particles, so it behaves more like a pure solvent. The solvent vapor partial pressure will be proportional to the vapor pressure as a pure liquid. Henry's is most accurate where the volatile solute has low concentration. When the volatile solute concentration is low, each molecule will be surrounded by solvent molecules, so the solute will no behave like pure solute. It's vapor partial pressure is NOT proportional to its behaviour in its pure form. In an ideally dilute solution, the solvent obeys Raoult's law and the solute obeys Henry's law. Both are approximations
which reactions are faster, SN1 or SN2, all else being equal?
SN1
which type of substitution reaction can sometimes lead to carbon skeleton rearrangement?
SN1 to increase the stability of the carbon skeleton
for which type of substitution reaction is nucleophilicity not important/
SN1, because the leaving group is lost independently of the action of the nucleophile
which type of substitution reaction leads to a racemic mixture?
SN1. the carbocation is planar and the nucleophile can attack from either side
which type of substitution reaction often involves reflux (boiling the solvent? why?
SN1. to provide the necessary energy for the formation of the carbocation
which type of substitution reaction leads to an inversion of configuration?
SN2
what is the formula for sulfite?
SO3^2-
what is the formula for sulfate?
SO4^2-
what would you react with a carboxylic acid to get an acyl chloride?
SOCL2, PCL5 or PCL3
define the first law of thermodynamics
The law of conservation of energy. energy cannot be created or destroyed. the change in energy to a system must equal the sum of heat flow and work done on the system
what equation is used for the transfer of electromagnetic radiation in quanta?
This equation can also be used to calculate the energy in a photon
what is a furanose?
a 5 member carbohydrate ring
what is a pyranose?
a 6 member carbohydrate ring
how does the presence of resonance in a conjugate base impact the acidity of the acid?
a base with resonance stabilization is a weaker base and since base strength is negatively correlated with acid strength, the weaker the base, the stronger the acid and vice versa
what do you call an object with an emissivity value of 1?
a black body radiator. these are possible only in theory and they absord 100% of incoming radiation, so they appear totally black
briefly explain newton's law of cooling
a body's rate of cooling is proportional to the temperature difference between the body and its environment
what is amylopectin?
a branched chain of glucose molecules. the main chain is made from alpha 1-4 glucosidic linkages and alpha 1-6 linkages form the branches
what is an aldose?
a carbohydrate that contains aldehydes
what is an aldol condensation reaction and how does it work?
a carbonyl nulceophile attacks another carbonyl. This is possible because an alpha carbon can act as the nucleophile. a new bond is formed between the alpha carbon of one molecule (which keeps its carbonyl) and the carbonyl carbon of the other molecule (which is reduced to an alcohol). This can occur when 2 aldehydes react, 2 ketones react or one of each reacts. the reaction can be catalyzed by acid or base. the initial product is an aldol, and after dehydration it becomes an enal, which is an alkene on the beta carbon
what is cellulose?
a chain of glucose molecules held together by beta 1-4 glucosidic linkages
what is the difference in the value you get from a coffee cup calorimeter and a bomb calorimeter?
a coffee cup calorimeter is a constant pressure calorimeter and gives you the heat of reaction (H), which can be found by plugging H in for q in the q=mcT equation. A bomb calorimeter is a constant volume calorimeter (no PV work), so it gives you the internal energy change when you use the equation q=CT
in terms of vapor pressure vs partial pressure, when does a compound evaporate?
a compound evaporates when the vapor pressure of its liquid phase is greater than the partial pressure of its gaseous phase. It condenses when this is reversed. For example, imagine a puddle of water on the road. In conditions of mild humidity, there will be some water in the air, so this water vapor will have a partial pressure. If the partial pressure of the water in the air and the vapor pressure of the water in the puddle are the same, they will be at equilibrium, and condensation and evaporation will be equal. If either the air dries out (less water pressure) or if the wind picks up (faster moving fluids have lower pressure), now the vapor pressure of the water in the puddle will be greater than the partial pressure of water in the air, so evaporation will occur. If the air slows down or gets more humid, the partial pressure of the water in the air could become greater than the vapor pressure of the water in the puddle, and condensation can occur.
what is a meso compound?
a compound with multiple chiral centers that is optically inactive. they have a plane of symmetry in them and the chiral centers cancel each other out in optical activity. they are considered achiral
what is a lactone and how are they formed?
a cyclic ester. formed when an alcohol attacks a carboxylic acid on the same carbon chain
describe the components of a galvanic cell
a galvanic cell is made of a multiphase series of components. Each component is present in only a single phase. All phases must conduct electricity and at least one phase must be impermeable to electrons, otherwise electrons would move freely through the circuit and equilibrium would be quickly reached. The phase that does not conduct electrons, must be an ionic conductor, which carries the current in the form of charged ions. This is usually an aqueous electrolyte solution (salt bridge). A simple galvanic cell contains 2 electrodes: the anode and the cathode. The 2 terminals (electrodes) must be made of the same material (i don't get this part).
what is lactose?
a glucose and galactose held together by a beta 1-4 galactosidic linkage
what happens in alpha decay?
a helium nucleus is lost (2 protons ans 2 neutrons). the mass number will decrease by 4 and the atomic number will decrease by 2. the new element will be 2 to the left on the p. table
what happens in gamma decay?
a high energy gamma ray is emitted. there is no change in either mass or atomic number
what is a gamma ray?
a high frequency photon. it has no mass and no charge
what is a solution?
a homogeneous mixture of 2 or more compounds in a single phase
what is a concentration cell?
a limited type of galvanic cell where a reduction half reaction takes place in one half cell, while the exact reverse of that half reaction takes place in the other half cell. adding the 2 half reactions gives E naught=0 (if both sides had the same concentration)
what is a molecule with multiple chiral centers but that is optically inactive called?
a meso compound
what happens in beta decay?
a neutron becomes a proton either by an electron being emitted or a positron being absorbed. there will be no change in mass number but the atomic number will increase by 1. the new element will be one to the right on the p. table
what is a cyanohydrin?
a nitrile and alcohol on the same carbon
what is the nucleus of a specified isotope called?
a nuclide
what type of solvent would you use if you wanted to increase the rate of an SN1 reaction?
a polar protic solvent. it stabilizes the carbocation and speeds up the rate
what is a polar protic solvent?
a polar solvent that can hydrogen bond
what is standard temperature and pressure (STP)?
a pressure of 1 atm and a temperature of 273 K (0 degrees celcius)
what is an isothermal process?
a process that occurs with no change to internal energy
what is a path function?
a property that depends on the pathway used to reach the current state such as heat and work
what is an intensive property?
a property that is independent of the size of the system ie pressure and temperature
what is an extensive property?
a property that is proportional to the system ie volume, number of moles, mass etc
what happens in positron emission?
a proton becomes a neutron and a positron in emitted. there is no change is mass number but the atomic number will decrease by 1. the new element will be 1 to the left on the p. table
what happens in electron capture?
a proton becomes a neutron and an electron is absorbed. there is no change in mass number, but the atomic number will decrease by 1. the new element will be one to the left on the p. table
what is the 3rd law of thermodynamics?
a pure element in its solid form at absolute zero and internal equilibrium will have an entropy value of zero. absolute zero can never be realized so this exists only in theory
what do you call a 6 member carbohydrate ring?
a pyranose, so glucose is glucopyranose
what is an elementary reaction?
a reaction that occurs in a single step. YOU CANNOT DETERMINE OF A REACTION IS ELEMENTARY OR NOT FROM ITS CHEMICAL EQUATION. DO NOT ASSUME UNLESS YOU ARE TOLD
what is a redox titration? How is it performed?
a reaction used to find the molarity of a reducing agent. A strong oxidizing agent it titrated and the resulting voltage is measured. (voltage is a potential difference, so for a solution to have a voltage, it must be compared to another solution, called a standard solution. When referenced to the standard solution, the solution with a reducing agent has a voltage. As the strong oxidizing agent is added to the solution, the voltage increases, at first gradually, then quite suddenly. This sudden shift is the equivalence point, where all the molecules of reducing agent have been oxidized. This can be measured with an indicator or a voltmeter. The number of moles of oxidizing agent required will either be equal to or a multiple of the moles of reducing agent, since the oxidizing agent may accept a different number of electrons than one molecule of the reducing agent gives up.
what is temperature?
a representation of the amount of molecular movement in a substance
what is the function of a salt bridge?
a salt bridge is a type of liquid junction that minimizes the added potential difference between a cell that uses 2 different solutions. A salt bridge will typically be KCl. The bridge allows movement of ions btw solutions without creating a strong extra potential withing the galvanic cell. It minimizes the difference between K+ and Cl- travel to the opposite terminal at approximately the same rate
what is the simplest form of a chiral molecule?
a single carbon bonded to 4 different atoms will always be chiral
what is a non-volatile solute?
a solute that has no vapor pressure
what is a volatile solute?
a solute with a vapor pressure
what is solubility?
a solute's tendency to dissolve in a solvent, usually measured in moles/ liter
what does a positive cell potential indicate?
a spontaneous reaction
what is amylose (starch)?
a straight chain of glucose molecules held together by alpha 1-4 linkages
what does strong acid or base mean?
a strong acid is stronger than H30+. a strong base is stronger than OH-. it is assumed that strong acids and bases completely dissociate in water
what is a catalyst?
a substance that increases the rate of a reaction without being consumed or permanently altered. they increase the rate of BOTH the forward and reverse reactions. Catalysts have NO impact on the equilibrium ratio of a reaction, it just gets a reaction to equilibrium more quickly
what is a reducing sugar?
a sugar with a hemiacetal or hemiketal group rather than an acetal or ketal. theya re susceptible to attack
on the MCAT, what is the only type of substrate that will undergo SN1 reactions?
a tertiary substrate
what is annihilation?
a type of antimatter collision where mass is destroyed and converted to energy in the form of gamma rays
how do the boiling points of ethers relate to those of similar weight alkanes?
about the same. ethers can't hydrogen bond to themselves, so they dont have the same kind of heightened boiling point as alcohols etc
at what pressure do gases start to deviate from ideal behaviour?
above 10 atm
what is the acid equilibrium constant in water called?
acid dissociation constant Ka
how does acidity trend in oxyacids? why?
acid strength increases as the number of oxygens increases. this is due to conjugate base stability. The oxygens pull electron density to one side of the molecule and they are able to stabilize the conjugate base by spreading out electron density
what is the most common reaction type on the MCAT for carboxylic acids?
acid-base reactions, though sometimes they undergo nucleophilic substitution
how can you differentiate acids and bases by touch / taste?
acids taste sour or tart and bases are slippery when wet
what is the most reactive type of carbonyl group and why?
acyl chlorides because the chloride pulls electron density away from the already positive carbonyl carbon
what is the most reactive carboxylic acid derivative?
acyl halides
how can you increase the rate of tautomerization?
add an acid or base catalyst
how do you make acetals and ketals?
add an additional alcohol to existing hemiacetals/ hemiketals. in order for the reaction to proceed past the hemi stage, the OH group needs to be protonated to make a good leaving group (water), so this needs to occur in acidic conditions. the reaction will stop at the hemi stage in basic conditions
how do you reverse a reaction where you used an acetal to protect an aldehyde group?
add proton source
how can you push a reaction to favor the thermodynamic product?
adding heat helps the reactant surpass the activation energy of thermodynamic reactions
aldehydes and ketones undergo what type of reaction when attacked by a nucleophile?
addition reaction (no leaving group so substitution cant occur)
how do you usually make esters?
alcohol undergoes nucleophilic substitution with a carboxylic acid, using a strong acid catalyst to protonate the OH group on the acid
which is more reactive, aldehydes or ketones and why?
aldehydes because the extra R group on ketones is electron donating which lessens the partial positive charge on the carbonyl carbon
what is the oxidation product of primary alcohols?
aldehydes, which in turn oxidize into carboxylic acids
what is a carbohydrate that contains an aldehyde called?
aldose
all metal cations with the exception of these act as weak lewis acids in aqueous solution
alkali metals and heavy alkaline earth metals ie Ca2+, Sr 2+ and Ba2+
compare the boiling points of alkanes, ketones/ alhedydes and alcohols of comparable weights
alkanes have the lowest boiling points because it is non polar and has the weakest intermolecular bonds. aldehydes/ ketones are more polar and thus have higher boiling points than alkanes, but they are unable to hydrogen bond to each other so they have lower boiling points than similar alcohols
how does the presence of alkyl groups impact acidity vs basicity?
alkyl groups are electron donating groups, meaning they stabilize positive charge, resulting in increased basicity and decreased acidity or alcohols for example. due to the presence of EDGs, methyl and primary alcohols are more acidic than tertiary alcohols
what is the absolute orientation of all amino acids and what are the exceptions?
all amino acids are L, except for cysteine which is R due to its S group and glycine which is achiral
how does the bonding of group 14 elements change in the presence of a Lewis base?
all group 14 elements can form four covalent bonds with non-metals, and all beyond the second period can form 2 additional bonds with lewis bases by using d orbitals
how does the bonding of group 15 elements change with lewis bases?
all group 15 elements can form 3 bonds, and all beyond the second period can form 2 more by using their d orbitals. lewis bases allow them to form a 6th bond
what are open systems?
allow the exchange of mass and energy with the surroundings
what type of linkage is used in amylose (starch)?
alpha 1-4 glucosidic linkages
what is the bond in maltose?
alpha 1-4 glycosidic linkage between 2 glucose molecules
what bonds hold the glucose molecules together in glycogen?
alpha 1-4 linkages make up the back bone and alpha 1-6 linkages make up the side chains
what is the most difficult carboxylic derivative to hydrolyse back into a carboxylic acid?
amides. the hydrolysis of amides can only happen under extreme chemical conditions ie high temp, strong acid etc
what is NH4+?
ammonium
what happens when 2 ring shaped monosaccharides undergo nucleophilic substitution with each other?
an acetal is formed. this is how you make polysaccharides
what is required to make enamine/ imine formation go to completion?
an acid catalyst to protonate and destabilize the intermediate, leading to a dehydration reaction
describe the stecker synthesis
an aldehyde (with the desired R group) is mixed with potassium cyanide and ammonium chloride. In the first step, the cyanide anion acts as a nucleophile toward the carbonyl, making a hydroxy nitrile. however, the N is a better nucleophile than O and acid protonates the OH group. in the second step, nucleophilic substitution occurs and an aminonitrile is formed. the nitrile acts like a carboxylic acid derivative. In the last step, the strong acid in water protonates the nitrile group, turning it back to a carboxylic acid. Voila, a new amino acid
what is the arrhenius theory of acids and bases?
an arrhenius acid is any substance that produces hydrogen ions in water and an arrhenius base is any substance that produces hydroxide ions in water
what is a lewis acid?
an electron acceptor
what is a lewis base?
an electron donor
what is hund's rule?
an electron will not fill any orbital in a given subshell unless all orbital already have at least 1 electron. this minimizes the amount of potential energy in the system
what is the final product of an aldol condensation reaction?
an enal
what is an enolate and how do you make them?
an enolate is a negatively charged enol. they are basic carbonyls and can act as nucleophiles. an enolate is produced when a ketone is in basic solution
what happens when an alcohol attacks a carboxilic acid?
an ester is made
what type of bond is used to link nucleic acids?
anhydride bonds that are called phosphodiester bonds
in what direction do the ions flow in a galvanic cell?
anions travel from the cathode TOWARDS the anode and vice versa through the aqueous solution
what is a lewis acid?
any substance that accepts a pair of electrons
what is a bronsted base?
any substance that accepts a proton
what is a lewis base?
any substance that donates a pair of electrons
what is a bronsted acid?
any substance that donates a proton
what is an arrhenius acid?
any substance that produces hydrogen ions in water
what is an arrhenius base?
any substance that produces hydroxide ions in water
what is the pKa of most fatty acids and what does this mean for their structure in the body?
around 4.5, so most exist in their anion form in the cellular environment
how are half reaction potentials listed?
as reduction potentials
explain why phosphoric acids are relatively stable in biological systems, given they have a very reactive PO double bond
at pH 7 (normal body pH), triphosphates exist as negative ions, which helps to stabilize the partial positive charge on the P, reducing its susceptibility to nucleophilic attack
temperature correlates with which molecular phenomenon?
atomic movement
describe the periodic trend of atomic radius
atomic radius generally decreases as you move up and to the right
differentiate between what gets oxidized/ reduced and the oxidizing/ reducing agents
atoms get oxidized or reduced but an oxidizing/ reducing agent is a compound, not an atoms, so in an imaginary reaction, Ni could be reduced, but only nickel in its compound form NiO2 can be the oxidizing agent
how can you tell what makes a good leaving group?
atoms with a greater number of electron shells or those that are resonance stabilized will be better able to distribute its charge. they make good leaving groups and poor nucleophiles. Also, weak bases are also good leaving groups. Also, atoms/ molecules that leave as gases like CO2 or N2 are great leaving groups, because they leave the solution and never come back, so they never compete with other nucleophiles
to act as bases, what type of solvent is needed by alcohols and amines?
basic or neutral solvent
why cant you use the henderson Hasselbach equation be used to find the pH at the equivalence point?
because it uses pKa to calculate pH. At the equivalence point, all moles of acid have been converted to the conjugate base, so pKb of the conjugate base must be used instead.
describe the process of titrating a weak acid with a strong base in terms of the concentration of HA in solution
before the titration begins, the concentration of HA in solution will be 100% (at low pH, weak acids are disinclined to deprotonate). as you add the strong base, more and more HA molecules will have their protons stripped away. At the half equivalence point, exactly half of the HA molecules will have had their protons removed and [HA]=[A-]. At the equivalence point, the strong base will have stripped all of the HA molecules of their protons and [A-]=100%
what is the linkage between glucose and galactose in lactose?
beta 1-4 galactosidic linkage
what type of radioactive decay are positron emission and electron capture?
beta decay
what is HC03^-?
bicarbonate
what are hydrides?
binary compounds containing hydrogen. they can be basic, acid or neutral
describe the physical and chemical trends of alcohols
boiling point increases with molecular weight and decreases with branching. melting point tends to increase with molecular weight, but not as well. branching has a less obvious effect on melting point than boiling point. Both boiling and melting points are considerably higher than the related alkanes due to the ability of alcohols to H-bond
which second period elements break the octet rule?
boron and beryllium
what is the difference between using lithium aluminum hydride and sodium borohydride in reduction reactions ?
both are strong enough to reduce aldehydes and ketones to alcohols by donating H-, but only LiAlH4 is strong enough to fully reduce carboxylic acids, esters and acetates to alcohols
what is glycogen?
branched chain of glucose where alpha 1-4 linkages make up the back bone and alpha 1-6 linkages make the side chains
give an example of a solid solution
brass. it is a solid solution of copper and zinc
how does fatty acid synthesis occur?
by aldol condensation between an acetyl-CoA molecule and a growing fatty-acyl chain on fatty acid synthase
how can you calculate emf?
by subtracting the potential of the reduction reaction at the anode (it is actually undergoing an oxidation reaction chemically speaking) from the potential of the reduction reaction at the cathode
how are pi bonds created?
by the overlap of p orbitals. the pi bond forms above and below the original sigma bond
how is rotational energy created?
by the rotation of a molecule around its center of mass. The center of mass remains fixed in place atoms in a monoatomic gas have no rotational energy
what is the difference btw C and c?
c is the specific heat capacity. it is an intrinsic property that represents the heat capacity per unit mass. C is heat capacity and it was an extrinsic property that depended on the size of the sample
what do you use mol fractions for in solution chemistry?
calculate vapor pressure
what are ketoses?
carbohydrates that contain ketones
what is the only group 14 element that can make pi bonds?
carbon
what is CO3^2-?
carbonate
what is the leaving group of anhydrides?
carboxylate ion
describe the trend of carboxylic acidity in water
carboxylic acids with 4 or less carbons are miscible in water, 5-9 are less soluble and more than 10 can be considered insoluble in water
how do you change the rate law when you need to include the concentration of catalyst?
catalysts require their own rate constant for the alternative pathway they provide, but they do not prevent the original reaction from proceeding at the same time. Therefore, you add the rate laws of the uncatalyzed and catalyzed reactions together to get the new combined rate law. Keep in mind that the rate of the original reaction will be negligible compared to the rate of the catalyzed reaction
what is the SI unit for luminous intensity?
cd (candela)
what do you get when you add a whole bunch of glucoses together in a straight chain?
cellulose
what is the prefix for 10^-2?
centi
what is the only factor that will change K, the equilibrium constant of a reaction?
changing the temperature
how do you find the pI for charged amino acids?
charged amino acids have a side chain that can act as an acid or a base so can be considered triprotic acids. They will have 3 pKa values. For acidic amino acids, the isoelectric point is the average of the 1st 2 pKas and for basic amino acids, it is the average of the second and third pKas
what do you call the condition when the rate of the forward reaction equals the rate of the reverse reaction?
chemical equilibrium
what is Cl03-?
chlorate
what is ClO2-?
chlorite
how do you make a buffer?
choose a weak acid with a pKa close to the desired pH, then add equivalent amounts of the acid and the conjugate base. Note* the concentration of the buffer solution should greatly exceed the amount of acid or base that could be added to affect the pH of the solution
how should you choose an indicator to use for a titration?
choose the indicator with the pKa as close as possible to the pH of the titration's equivalence point
which are less stable, cis or trans isomers and why?
cis isomers are less stable. their substituents are on the same side, leading to crowding and steric hindrance, which increases the energy level and decreases stability
which have higher boiling points, cis or trans isomers and why?
cis. they have a dipole moment and therefore stronger intermolecular bonds
what important biological reaction involves a retro aldol reaction?
cleavage of ATP activated glucose
what is the name of a system that can only exchange energy, not mass?
closed system
what are electrolytes?
compounds that form ions in aqueous solution
what is the name of the phase change from gas to liquid?
condensation
what type of isomer is not really an isomer?
conformational isomers, because they are just different orientations of the same molecule in space, caused by rotating around a single bond ie eclipsed, staggered, gauche etc
in what direction will current flow in a concentration cell?
consider that nature tends to increase entropy. Electrons will flow in the direction that allows the concentration in the half cells to become equal. they will flow towards the side that has the greater concentration of positive ions, since the electrons will cause the positive ions to become neutral and add to the electrode. current flows in the opposite direction of the electron flow.
what are the 2 types of calorimeter? Give an example of each.
constant pressure and constant volume calorimeters. A coffee cup calorimeter is an example of a constant pressure calorimeter that measures energy change at atmospheric pressure (they are insulate to prevent energy exchange with the surroundings but they are open at the top so that pressure is constant, they measure heat of reaction H, which is equal to q). a bomb calorimeter is a constant volume calorimeter (no PV work allowed, so it gives the internal energy change of the reaction, since without work E=q. the equation q=Cdelta T is used)
how does solubility react to temperature change?
contrary to Le Chatelier's principle, increasing temperature even of exothermic liquid/ solid solution reactions increases the solubility. This is because by increasing the temperature, you increase the impact of the entropy term in the G=H-TS equation, so the reaction is pushed further towards spontaneity as temperature rises. In contrast, when a gas dissolves in a liquid, the entropy is decreased and solubility will be reduced as you increase temperature
what is the SI unit for charge?
coulombs
what are anomers?
cyclic diastereomers that are formed when a ring closure occurs at an epimeric carbon. the chiral carbon is now called an anomeric carbon
what is the difference between dark and light colours with respect to their reaction to radiation?
dark colours tend to absorb and radiate better than light colours, which tend to reflect radiation
what is the prefix for 10^-1?
deci
what king of reaction would you use to bind 2 reducing sugars together?
dehydration (technically acetal formation)
how can you make alkenes from alcohols?
dehydration, which is an elimination reaction
in an adiabatic ideal gas process, what are the values of E, q and w from the first law of thermodynamics equation?
delta E=q+w. in an adiabatic process there is no heat transferred, so q=0 and E=w (all change in internal energy is due to work)
what is the equation for spontaneity in galvanic cells?
delta G= -nFEmax, where n is number of moles of electrons transferred in the balanced redox rxn, F is the charge of 1 mole of electrons (96 486 C/mol). The equation basically says that the free energy is the product of the total charge (moles x charge per mole) and the voltage E (the product of charge and voltage is electrical work, a type of non-PV work?
What factor causes gases to separate?
density. due to the force of gravity, denser gases will settle beneath less dense gases and you will then be able to distinguish them. In general, colder gases will be heavier (more dense) than warmer ones because their molecules have less energy and will be more compact
compare the specific heats of the same element/ compound in different phases
depending on the phase, the specific heat will change. Gases have almost no intermolecular forces, so almost all of the heat energy goes directly to increasing kinetic energy and therefore temperature. solids have much stronger intermolecular forces, and therefore some of the heat energy will be expended as the atoms stretch their bonds. The specific heats follow this trend: Gases<Liquids< Solids
what is the name of the phase change from gas to solid?
deposition
what is an epimer?
diastereomers that differ at only one chiral carbon
what is sucrose?
disaccharide made from glucose and fructose with a 1,2 glycosidic linkage that is alpha for glucose and beta for fructose
how do you get an intensive property?
divide one extensive property by another
what is the shape of p orbitals?
dumb bell shaped. organized along the x, y or z axis
what can happen when a ketone is asymmetric about the carbonyl carbon?
during keto enol tautomerization, 2 different enolates can be produced: the kinetic enolate and the thermodynamic enolate
what can be added to water to make it a better conductor?
electrolytes (they form ions in aqueous solution)
describe the relationship between electronegativity and nucleophilicity
electronegativity is the tendency of an element to hold onto its shared electrons close to the nucleus, whereas nucleophilicity is the tendency to share its electrons. They therefore follow opposite trends so increased nucleophilicity is associated with decreased electronegativity. Across a row in the periodic table (left to right), nucleophilicity decreases, whereas electronegativity increases. So RH2C- would be the best nucleophile > RHN- >RO- would be the worst
in a reaction, what component of internal energy accounts for the greatest change in internal energy?
electronic energy, the potential energy between electrons and their nuclei
what is the aufbau principle?
electrons add to the lowest energy level first
are electrophiles lewis acids or bases and why?
electrophiles are lewis acids because they are electron acceptors
what does quantum mechanics say about elementary particles and energy?
elementary particles can only gain or lose energy in discrete units/ quanta
what are diamagnetic elements?
elements with no unpaired electrons, meaning their subshells are completely full. they do NOT respond to external magnetic fields
what are paramagnetic elements?
elements with unpaired electrons ie Li, meaning that a sub shell is not completely filled. the spin of each unpaired electron will be parallel to the others, meaning they will align with an external magnetic field
what 2 functional groups demonstrate tautomerization?
enamines and imines
what are the 2 types of stereoisomers?
enantiomers and diasteriomers
what does endergonic mean on the MCAT?
endergonic means the reaction has positive delta G and is non-spontaneous
a reaction with a positive enthalpy change is what type of reaction?
endothermic
what happens to the energy of the system in contraction?
energy is transferred into the system. delta E is positive
what happens to the energy of the system in expansion?
energy is transferred out Delta E is negative
how are enthalpy values assigned?
enthalpy is a made up piece of shit idea so it has no absolute values associated with it. Scientists arbitrarily chose to give an element in it's standard state at 25C and enthalpy value of 0 kJ/ mol. (keep in mind that the standard state will be the reference form ie the most stable version of that element at the given temperature, so for N it would be gaseous N2). Enthalpy values are assigned to compounds based on their change in enthalpy when they are formed from raw elements in their standard states at 25C.
what is enthalpy?
enthalpy is an equation rather than a property. it is defined as the systems internal energy plus PV. enthalpy is measured in Joules, but unlike energy, enthalpy is not conserved. the enthalpy of the universe doe NOT remain constant. Enthalpy is an extensive state function and in ideal gases it is dependent only upon temperature
what is the driving force that determines if a reaction can proceed?
entropy
what type of property is entropy?
entropy is a state function and an extrinsic property
what happens to entropy and thermodynamics at the microscopic level?
entropy is undefined and the laws of thermodynamics do not apply without the statistical modelling of a large number of molecules. Thermodynamics is about the average behaviour of thousands/ millions etc of molecules/ atoms
what are diastereomers that differ at only one chiral carbon called?
epimers
describe an esterification reaction and some problems it can face and how you would solve them
esterification is the synthesis of an ester by combining a carboxylic acid and an alcohol in the presence of a strong acid catalyst. the yield is low because the strong acid also protonates the reverse reaction. This can be counteracted by adding excess water or alcohol according to Le Chatelier's principle
what type of reaction are you performing if you react an alcohol and a carboxylic acid in the presence of a strong acid?
esterification. the products are an ester and water
what is the more formal name for acetic acid?
ethanoic acid
what is the most common solvent used in the MCAT?
ethers
what is the half equivalence point on a titration curve?
exactly half of the acid has been neutralized by the base. In other words, the concentration of the acid is equal to the concentration of its conjugate base
what does exergonic mean on the MCAT?
exergonic means the reaction has negative delta G and is spontaneous
a reaction with a negative enthalpy change is what type of reaction?
exothermic
what types of properties can be used to describe the macroscopic state of a system?
extensive and intensive properties
what important biological reaction aldol condensation?
fatty acid synthesis
what is the prefix for 10^-15?
femto
what elements can hydrogen interact with to form hydrogen bonds?
fluorine, oxygen and nitrogen
what is the least acidic hydrogen halide? why?
fluorine. its bond is the most polar, which should contribute to its acidity, but its actually so polar that the atoms are hydrogen bonded together also, F- has a very concentrated charge and is much too strong of a conjugate base
what is a standard state?
for a pure solid or liquid, the standard state is the reference form of a substance at any chosen temperature T and a pressure of 1 bar (10^5 pascals). the reference form is usually the form that is most stable at 1 bar and the chosen temperature
what is the simplest carboxylic acid?
formic acid
what is the name of the phase change from liquid to solid?
freezing
where do the hydrogen and hydroxide ions usually come from in acid base reactions?
from the aqueous solvent
what do you call a 5 member carbohydrate ring?
furanose
what is another way to consider amu (atomic mass unit)?
g/mol. in biochemistry it is a dalton
discuss the spontaneity of galvanic cells, concentration cells and electrolytic cells
galvanic cells and concentration cells will always be spontaneous and their G value will be negative. Electrolytic cells are non-spontaneous and their G will be positive
what is the difference in cell potentials in galvanic and electrolytic cells?
galvanic cells have positive emf on the MCAT and electrolytic cells have negative emf
what is Henry's law?
gas law that states that the solubility of a gas in a liquid at constant temperature is proportional to the partial pressure of that gas over that liquid, ie increasing pressure increases the solubility of that gas
how does external pressure impact the phase behaviour of molecules?
gases and solids are on opposite extremes of the pressure spectrum, with liquids in the middle. If there is low external pressure, it is easier for molecules to spread out and limit their interactions with each other, which favors gases. if external pressure is very high, molecules get compacted and squeezed together more and this favors solids
what conditions favor the gas phase?
gases are favored when temperatures are high and each molecule has the energy to break free of its intermolecular forces. Gases are also favored when pressure is low and molecules have the ability to spread out
what is the periodic trend in ionization energy?
generally increases up and to the right
what are the building blocks of sucrose?
glucose and fructose
which is the only non-chiral amino acid?
glycine
what is the difference between grignard reactions and hydride synthesis, given that they are both used to make alcohols?
grignard reactions use organometallic reagent to make an alcohol and extend the carbon chain. in hydride synthesis, the chain remains the same length
describe the grignard synthesis of an alcohol
grignard reagnets are organometallic compounds which are super potent bases and nucleophiles, even more than oxygen or nitrogen ions. the organometallic reagent is made from a super polarized carbon-metal ionic bond. in the first step, the carbon metallic bond is broken and the carbon adds to the carbonyl, releasing the metal ionic bond, which goes and interacts with the oxygen ion. adding a proton source results in the formation of an alcohol. This is a great way to lengthen carbon chains, since it is the carbon that adds to the carbonyl, not the metal
which group of transition metals react to give a +1 charge?
group 11
what are the only 2 ways to transfer energy between systems?
heat (q) and work (w). heat is the spontaneous transfer of energy from a warmer body to a colder body. any energy transfer that is not heat is work
what is the relationship btw heat and enthalpy?
heat and enthalpy are not the same thing. heat only equals enthalpy at constant pressure
what is the enthalpy associated with melting called?
heat of fusion
what is the term usually used for the change in enthalpy from reactants to products?
heat of reaction
what is the enthalpy associated with vaporization called?
heat of vaporization
which is usually greater and why, the heat of fusion or heat of vaporization?
heat of vaporization is usually larger, since it takes more energy to transition from liquid to gas than from solid to liquid (more significant intermolecular bond breaking)
when heat is measured by a calorimeter, how does that relate to delta H?
heat will be negative delta H
what happens when an alcohol attacks an aldehyde?
hemiacetal
what happens when an alcohol attacks a ketone?
hemiketal
what are the 2 types of catalysts?
heterogeneous (different phase) and homogeneous (same phase) catalysts
in gases, how does pressure impact the rate constant?
higher pressure means faster reaction (higher k)
is autocatalysis an example of heterogeneous or homogeneous catalysis?
homogeneous. a product of the reaction acts to catalyze the reaction
how do you make an electrolytic cell?
hook up a power source across the resistance of a galvanic cell and force the reactions to run in reverse. Any galvanic cell on the MCAT will have a negative emf. The cathode is marked negative and the anode marked positive
what does the reaction rate actually describe?
how quickly the concentration of the reactants or products are changing over the course of the reaction
describe the acid base trends of hydrides
hydrides can be acidic, basic or neutral. the basic hydrides are found on the left of the periodic table and the acid hydrides on the right. this trend tells us that metal hydrides are either basic or neutral and non metal hydrides are either acidic or neutral ** NH3 is the exception**. the acidity of non-metal hydrides increases as you go down the table
what is the strongest type of intermolecular force?
hydrogen bond
what is ClO-?
hypochlorite
What is Avogadro's law?
ideal gas law that says that the volume of a gas is proportional to the number of moles at constant temperature and pressure. V/n= constant
what does the relationship between K and delta G naught say about spontaneity?
if K is larger than 1, the value for delta G naught will be smaller than one, but this does NOT necessarily mean that any reaction with an equilibrium constant greater than 1 will be spontaneous, it only means that a reaction that has an equilibrium constant greater than 1 is spontaneous at the specific temperature used to derive that particular equilibrium and standard state. Simply seeing an equilibrium constant on its own is not sufficient to determine spontaneity
what do you need to keep in mind if you use a fischer projection to determine absolute configuration?
if the lowest priority bond was coming out of the page (horizontal), the R or S designation will need to be reversed to find the actual orientation. so R becomes S and S becomes R
what can the exo/ endothermic nature of a reaction tell you about the stability of the intermolecular bonds in the solute/ solvent/ solution?
if the overall reaction (not individual steps) releases energy, the new intermolecular bonds between the solvent and solute are more stable than the original ones and the intermolecular attractions between and solvent and solute are stronger that between molecules of the pure substances. Lower energy of a system usually indicates higher stability. A negative heat of solution indicates stronger bonds and a positive heat of solution indicates weaker bonds
what is vapor pressure?
if you have a vacuum sealed container partly filled with liquid, the space above the liquid will be occupied by vapor particles that had enough kinetic energy to leave the liquid and enter the gas phase. Some of those gas particles will lose their energy and condense back into the liquid. Eventually an equilibrium will be reached and at this point, the pressure exerted by the gas molecules in the space above the liquid is called the vapor pressure of the liquid
what does the positive/ negative value of a heat of solution tell us about how thee vapor pressure will change in a non-ideal solution?
in a non-ideal solution, you can't really use Raoult's law, because the intermolecular forces in the solvent and solute will behave differently than in an ideal solution and will require more or less energy to break and allow gas molecules to be free. If the reaction has a negative heat of solution when the solute is dissolved, that means that energy was released from bonds forming, ie the intermolecular bonds in the solution are stronger than for the pure substances. In that case, it would require MORE energy to free gas molecules, and so the vapor pressure would be reduced because there would be fewer gas molecules to exert pressure on the surface of the liquid. If the heat of solution was positive, it means energy was required during dissolution to break bonds, and the intermolecular forces in the solution are weaker than in the pure substances. This means that it would take LESS energy to free the gas molecules and the vapor pressure would be GREATER. Negative heat of solution: reduced vapor pressure positive heat of solution : increased vapor pressure
briefly describe the equipartition theory
in a normal system, each mode of translational motion (x, y, z) should have the same average energy. The energy of each mode should be equal to 1/2 kT, where T is the temperature and k is the Boltzmann constant (1.38 x 10^-23 J/K
what are the requirements for a compound to be aromatic?
in addition to the normal requirements for resonance, aromatic compounds must be cyclic, planar and follow Huckel's rule: 4 n+ 2 pi electrons
how can you tell between alpha glucose and beta glucose?
in alpha glucose, the OH group on the anomeric carbon (C1) and the OH group on the methoxy group (C6) are on opposite sides of the rings structure, whereas in beta glucose, they are on the same side
how can you tell if a linkage in a carbohydrate is alpha or beta?
in alpha, the bond will be on the opposite side of the ring from the sticky uppy group, in beta, they will be on the same side
in an isovolumetric ideal gas process in a flexible container, what are the values of E, q and w from the thermodynamics equation?
in an isovolumetric process, there is no change in volume, so no work was done w=0. any change in internal energy is therefore due to heat transfer E=q
what is the relationship between Ea and the rate constant?
in the Arrhenius equation, Ea is a negative exponent, which indicates that as you increase Ea, you decrease the rate constant k. This makes sense since a lower k means a slower reaction and as you raise the Ea, fewer and fewer collisions will meet the energy requirements and the reaction will by necessity proceed more slowly
when does keto enot tautomerization normally occur in biological systems?
in the bases of nucleotides
Describe the Process of the Gabriel synthesis.
in the first step, a nitrogen is protected by a phthalimide (di-amide) to prevent more than one alkylation from occurring. N acts as a nucleophile and substitutes the bromide on the diethyl bromomalonate. in the enxt step, something very rare happens and the central carbon loses a hydrogen and becomes a carbanion (strong nucleophile) that is stabilized by the 2 carboxylic acids on either side. the carbanion undergoes nucleophilic substitution with an alkyl halide (to make the R group). in the final step, nitrogen is hydrolyzed from the phthalimide by acid and water.
describe the process of a base catalyzed aldol condensation reaction
in the first step, the base removes an alpha hydrogen from one of the aldehydes/ ketones , leaving an enolate ion. The enolate ion then acts as a nucleophile (the carbon, NOT the oxygen) and attacks the other carbonyl carbon, creating an alkoxide ion. the alkoxide ion removes an H from water, producing the aldol. the dehydration occurs when the base abstracts the second alpha hydrogen (making water) and a double bond forms at the beta hydrogen, and kicking out OH- as the leaving group (this is a weaker base than the alkoxide ion so its fine)
describe nucleophilic addition to aldehydes/ ketones under ACIDIC conditions
in the presence of acid, the oxygen of the carbonyl group is protonated in the first step, making it more electrophilic. a nucleophile then attacks the protonated carbonyl group, resulting in the formation of an alcohol with the nucleophile attached to the former carbonyl carbon
describe hoe imine and enamine formation occurs
in the reaction of an amine with an aldehyde or a ketone, the amine acts as a nucleophile, attacking the partially positive carbonyl carbon. A tetrahedral intermediate is formed and an acid catalyst protonates the product to create an unstable intermediate. a dehydration reaction then takes place and water is lost, producing either an imine or an enamine. if the original amine was primary or had no constituents, an imine will form. if more than one R group was present, the nitrogen can't afford a double bond to carbon, so the carbonyl gives up one of its alpha hydrogens to produce the CC double bond of the enamine. tertiary amines dont have a proton to lose in the first step, so they do NOT add to carbonyls
hoe do diasteriomers differ from each other?
in their physical properties (rotation of polarized light, melting point, boiling point, solubility etc) and chemical properties
what is the periodic trend for electron affinity?
increases up and to the right. in terms of exothermicity (energy RELEASED when an electron is added), electron affinity increases in exothermicity (atoms get more stable when an electron is added) as you move up and to the right. exothermicity may be shown with a negative sign
how do charge and molecular size impact solubility?
increasing size and charge tend to decrease solubility
what changes can be made to a solid catalyst to make it more effective?
increasing the surface area increases the number of molecules that can react with the catalyst. Often this works by grinding a solid catalyst into a powder
in a closed system at rest with no electric or magnetic fields, the only energy change will be what?
internal energy
what is the name of a system that can exchange neither mass nor energy?
isolated system
how does the equilibrium equation change when you are dealing with gases?
it can be written in terms of partial pressures instead of concentrations and the result will be Kp, the partial pressure equilibrium constant
how can methane have 4 equivalent sigma bonds with hydrogen if it has 2 electrons in the s orbital and 2 electrons in the p orbital?
it can't. in order to have 4 equivalent bonds, the electrons in carbon occupy HYBRID sp3 orbitals so all of the electrons are at the same energy level. hybrid orbitals average out the contributions of the original s and p orbitals
how does entropy change for gases dissolving into liquids?
it decreases
how does nucleophilicity change across a row?
it decreases
what is the bronsted-lowry theory of acids and bases?
it defines as acid as any substance that donates a proton and a base as any substance that accepts a proton
how many carbon are in a fatty acid?
it depends but they are ALWAYS even numbered
do you need to include the concentration of catalyst in your rate law equation?
it depends. if the concentration of catalyst is low compared to substrate, adding more catalyst would increase the rate even more, so the concentration should be included in this case. if the concentration of catalyst is in excess to the substrates, adding more catalyst will not increase the rate of reaction, so you dont need to include the concentration of the catalyst.
are aldehydes and ketones soluble in water?
it depends. the aldehyde/ ketone functional group is polar, so when the carbon tail is short (4 carbons or less) they can dissolve in water. Any more carbons and the molecule loses its polarity and becomes insoluble
what happens when an atom is reduced?
it gains electrons
what happens to the reducing agent?
it gets oxidized
what happens to the oxidizing agent?
it gets reduced
what happens to bond length when a sigma bond becomes a pi bond?
it gets shorter. the atoms are held more closely together
what happens to atomic radius when you ADD an electron?
it grows. the increase in the ration between negative and positive charge means the positively charged nucleus pulls less strongly on the valence electrons. Also, increasing the negative charge increases the repulsion between the electrons, further pushing them apart
how does entropy change for solids dissolving into liquids?
it increases
what is the binding energy of an atom?
it is a measure of the stability of the nucleus. it is the energy that would be required to break the nucleus into individual protons and neutrons
what does the shape of orbitals represent?
it is a probability function. you have a 90% chance of finding and electron within the given shape of the orbital
what is Le Chatelier's principle?
it is a rule that can be used to predict how a system at equilibrium will respond to changing conditions. It states that when a system at equilibrium is stressed, the system will shift in a direction that will REDUCE that stress. There are 3 types of stress that obey Le Chatelier's principle: 1. Adding or removing products or reactants 2. changing the pressure/ volume of the system 3. heating or cooling the system. Systems like to be at equilibrium and when stressed, will react to reduce that stress by replacing what has been removed or reducing what was added etc
what is special about Gibbs free energy?
it is a way of incorporating the entropy change in both the system and surroundings into a single equation that only requires information about the system
what is the Haber process?
it is an all gas reaction that is used to generate fixed ammonia and it is very useful in the production of ammonia for fertilizer. it is an exothermic reaction
what is the cage effect?
it is an effect of solvation that is determined by the viscosity of the solvent. Reactant molecules get trapped in cages of solvent and are unable to collide with reactant molecules unless they are coincidentally trapped in a solvent cage with another reactant. It decreases the rate of reactant-reactant collisions to about the rate of collisions in gases
what is a galvanic/ voltaic cell? How does it work?
it is an electrical cell that turns chemical energy into chemical energy. If 2 electrically conducting things are placed in contact and a charged species from either cannot flow freely to the other one, a tiny amount of charge difference may result. This difference creates an electric potential between the things. The galvanic cell offers an alternative pathway for the electrons to travel between the things. The electric potential generates a current from ont phase to another in conversion of chemical energy into electrical energy
what does - or L mean in the name of a molecule?
it is optically active and rotates plane polarized light to the left
what does a + or D mean in the name of a molecule?
it is optically active and rotates plane polarized light to the right
what do you call a compounds that is hydrated?
it is said to be in aqueous phase
what is the significance of 1 cal?
it is the amount of energy required to raise 1 gram of water by 1 degree celcius
what is an absorption spectrum?
it is the characteristic radiation that is absorbed when electrons of an element absorb energy to move to a higher energy level
what happens to an atom when it is oxidized?
it loses electrons
what happens to atomic radius if you REMOVE an electron?
it shrinks: the positive charge of the nucleus pulls more strongly on the negatively charged electrons, drawing them in. also the loss of a negative charge decreases the repulsive force the electrons have on each other
what happens to the rate constant over the course of a reaction?
it stays the same. it is called the rate CONSTANT
in a redox reaction, what happened to the atom that lost electrons?
it was oxidized
in a redox reaction, what happened to the atom that gained electrons?
it was reduced
what is the pI for an acidic amino acid?
it will be the average of its first 2 pKas
what is the pI for a basic amino acid?
it will be the average of the second and third pKas
what will the pH at the equivalence point be for a weak acid, weak base titration?
it will depend on the specific acid and base used. If the acid was stronger than the base( pKa acid lower than pKb base), the pH would be below 7. if the base was stronger than the acid, the pH will be greater than 7
what sign will the anode have on an electrolytic cell? what type of reaction will occur there?
it will have a positive sign, but oxidation will still occur there
if you change the concentration of something in a reaction, according to Le Chatelier's principle, what happens to the reaction?
it will proceed in the direction of the less concentrated side
what would happen if you were to react an alcohol with permanganate (MnO4)?
it would oxidize all the way to a carboxylic acid
what would happen to your SN1 reaction if you used a polar aprotic solvent?
it would slow down
what would happen to your SN2 reaction if you used a polar protic solvent?
it would slow down
how do you determine the pH of a strong acid or base solution.
it's way easier than for weak acids. It is assumed that they completely dissociate in aqueous solution, so there will be none of the original strong acid or base to participate in the Ka/ Kb equation. You can't divide by zero, but since all of the initial acid or base is gone, we know they went entirely to making H3O+ or OH-. For example. If you had 0.001M solution of HCl, all the HCl would disappear and you would now have 0.001M H3O+. the hydronium ion concentration is now 0.001 or 10^-2 and -log(10^-2)=2, so the pH will be 2. if you're doing this with bases, remember that you'll get the pOH, so you need to subtract your answer from 14 if youre looking for the pH
what is an object's thermal conductivity (k) dependent upon?
its composition and to a much lesser extent, its temperature
what is the equation for the rate constant, k, of a reaction (Arrhenius equation)?
k= zpe^(-Ea/RT), where z is the collision frequency, p is the fraction of collisions with the right orientation, e is the fraction of collisions having the right energy, Ea is the activation energy and R is the gas constant 8.314 J/K mol
in what form to ketones and aldehydes exist in at room temperature?
keto-enol tautomers
what is the oxidation product of secondary alcohols?
ketones
what is a carbohydrate that contains a ketone called?
ketose
what is the SI unit for mass?
kg
what is the prefix for 10^3?
kilo
what are cyclic amides called?
lactams
what are cyclic carboxylic acids called?
lactones
what do you get if you combine glucose and galactose?
lactose
give the simple definition of metals
large atoms that tend to lose electrons to form positive ions and positive oxidation states. they can be thought of as atoms in a sea of electrons
what characteristic reduced nucleophilicity?
large size and electronegativity
how does molecular size impact entropy among molecules that are in the same place and at a given temperature?
larger molecules will have greater entropy (more bonds, more potential to spread energy)
if K<1 what is the value of delta G naught?
larger than 1
what is Raoult's law?
law that deals with vapor pressure in solutions. Adding non-volatile solvents will decrease the vapor pressure of a solution compared to its vapor pressure in pure solvent form. Raoult's law allows you to calculate the new vapor pressure of the solution by multiplying the mole fraction of the solvent (liquid) with the vapor pressure of the pure solvent Pv= XaPa Think of it this way: if 97% of the solution is solvent, then the new vapor pressure will be 97% of the vapor pressure of the pure solvent
at what water solubility value are compounds considered insoluble?
less than 0.01 mol/L
how does gibbs free energy differ from energy in an isolated system?
like enthalpy, gibbs free energy is NOT conserved in the sense of conservation of energy. the gibbs free energy of an isolated system can change
what is the reaction that breaks down triglyceridescalled?
lipolysis or saponification (if it is base catalyzed)
do liquids or gases have more collisions per second?
liquids have 100x more collisions per second than gases, because their molecules are much closer to each other
how do you name anhydrides?
list the 2 acids from which they were made alphabetically, drop the word acid and add 'anhydride'. example: propanoic acid and butanoic acid would be butanoic propanoic anhydride. Note: if the same acid makes up both sides of the anhydride, the name is NOT doubled, as in acetic anhydride
what are the ideal conditions for sublimation/ deposition?
low temperature and pressure. liquids can only exist at intermediate temperatures and pressures
how can you push a reaction towards favoring the kinetic product?
low temperatures prevent the reactant gaining enough energy to undergo the thermodynamic reaction and bulky bases have difficulty reaching the internal structure of a molecule, which will also favor the kinetic product
what conditions favor solids?
low temperatures, when molecules usually lack the energy to break their intermolecular bonds and high pressures, when molecules are packed tightly together
stronger acids have _______ pka
lower
what are the characteristics of metals?
lustrous, malleable, ductile, thermally and electrically conductive
what is the SI unit for length?
m
what are the representative elements?
main group elements in families 1, 2, 13, 14, 15, 16, 17 and 18. these are in group A of the old numbering system
what is the role of the slat bridge in the galvanic cell?
maintain the neutrality of the half cell. For example, as the cathode receives electrons, it will lose anions, which will travel to the cathode to replace the negative charge that was lost in ejecting an electron. The salt bridge allows anions to migrate so that the charge of the half cells remains a zero as the cell discharges
what is the Gabriel synthesis used for?
making amino acids de novo
what is the strecker synthesis used for?
making amino acids de novo
what do you get when you add 2 glucose molecules together?
maltose
what is the prefix for 10^6?
mega
what is the name of the phase change from solid to liquid?
melting
what is the prefix for 10^-6?
micro
what is the prefix for 10^-3?
milli
what is the conversion between mmHg, torr and atm?
mmHg and torr are equivalent and so 760 mmHg or 760 torr is equal to 1 atm
what is the SI unit for amount of substance?
mol
what is molarity?
mol/L
what is the normal unit used for rates of reaction?
mol/Ls
what do you call the measurement that is moles/ volume?
molarity
volume correlates with which molecular phenomenon?
molecular bonding
pressure correlates with which molecular phenomenon?
molecular forces
what is the difference in solubility of salts and gas with respect to size?
molecular size decreases the solubility of salts in liquid, whereas increased size in gas molecules increases solubiltiy. This is because the alrger the gas molecule, the greater its Van Der Waal forces anf the more soluble it becomes
what makes a good leaving group?
molecules that are stable when they leave (r at least more stable than the nucleophile was at the beginning of the reaction. weaker bases make for good leaving groups. electron withdrawing effects and polarizability also make for good leaving groups
what is mole fraction?
moles of a compound divided by the total moles of all species in a solution. It is a ratio and so has no units. Used to calculate the vapor pressure of a solution
what is molality?
moles of solute divided by kilograms of solvent. Usually has units of mol/ kg. It is used to calculate freezing point depression and boiling point elevation m= mol solute/ kg solvent
what is molarity?
moles of solute divided by the volume of the solution. Usually has units of mol/L M= moles/volume
discuss how size and charge impact solubiltiy
more charge and larger size decrease solubility. Ionic compounds composed of a cation and anion that have a single positive and negative charge respectively are usually soluble in water. compounds containing 2+ cations are less likely to be soluble. Size also makes a difference. Smaller ions or molecules suck as those containing group 1 metals are soluble, while compounds containing large heavy cations are less soluble
compare the solubility of organic compounds in ethers compared to alcohols
more soluble in ethers because no H bonds need to be broken for them to dissolve in ethers. Also, ethers are usually less polar than alcohols and most organic compounds are relatively non-polar. so like dissolves like
what is special about the first equivalent point of amino acids?
most amino acids have 2 equivalence points, one for the carboxylic acid end and one for the amino end. At pH below the first equivalence point, all of the hydrogens will be present on the amino end (there will be a + charge) and some of the protons will be present on the carboxylic acid end (uncharged, or less than a full negative charge). When the equivalence point is reached, all of the hydrogens will have been lost from the acid end and there will be a full - charge on the acid and of the amino acid and a full + charge on the amino end. This presence of dual charge is the isoelectric point (net charge = ) and the amino acid is called a zwitterion
compare the effectiveness of catalysts in the lab and the catalysts used in the human body
most enzymes in the body are way more effective than enzymes used in the lab. This is due to their greater specificity. A single active site can catalyze 1000 reactions per second, and the most effective can be thousands of times faster than those
what will be the pH at the equivalence point of a strong acid, strong base titration?
most likely pH=7
what is the significance in the distinction between D and L sugars
most naturally produced sugars are D epimers. As a result, enzymes for carbohydrate metabolism can't recognize L sugars and so they cant be digested/ used by the body
why do we usually only calculate the rate of reaction using the initial rate?
most reactions exist in some fore of equilibrium, where the products, once formed and able to react and transform back into the products, even as the forward reaction is still proceeding. Since rate equations rely on concentrations, we use the initial rate since there are only reactant and no (or very little) product, so we avoid the confusion
what is a molecular formula?
mostly used for molecular compounds, it shows the exact number of elemental atoms for each molecule
what is the prefix for 10^-9?
nano
what is the sign of the enthalpy change in an exothermic reaction?
negative
what are 2 characteristics that INCREASE nucleophilicity?
negative charge and polarizability
what is NO3-?
nitrate
what is NO2-?
nitrite
what are the only group 15 elements that can make pi bonds?
nitrogen and phosphorus, but they are weaker in phosphorus
what is special about nitrogen compared to other group 15 elements?
nitrogen is able to make a 4th bond despite the lack of d orbitals by donating its lone pair to form a bond
which is a better nucleophile, all else being equal, nitrogen or oxygen and why?
nitrogen is better since it shares its electrons more freely, bonds well and doesn't want to leave. it is more nucleophilic than oxygen, partly because it is LESS electronegative
what are isolated systems?
no exchange of mass of energy is possible
what is an adiabatic process?
no heat is transferred between the system and the surroundings
what is the Pauli exclusion principle?
no two electrons in the same atom can have the same 4 quantum ID numbers
at constant pressure, the enthalpy change of a system at rest is a measure of what?
non PV work and heat
what is an enantiomer?
non-superimposable mirror images of one another ie they are chiral
what is the measurement of concentration for polyprotic titrations?
normality. the normality is similar to concentration, but it actually is a measure of the acid or base equivalents per liter. So a 1 M solution of H2SO4 will have a normality of 2 since it has 2 protons to donate.
what happens to temperature if you combine 2 identical systems? Why?
nothing changes. temperature is an intensive property and as such is independent of the size of the system. Even though the energy in the system would double by adding the second system, the number of moles would double as well, so the average energy per mole would stay the same
what happens to pH when you add a small amount of water to a buffered solution?
nothing. The pH will not change
are nucleophiles lewis acids or bases and why?
nucleophiles are lewis bases because they donate electrons
what reaction that is favored by aldehydes and ketones is NOT possible for carboxylic acids?
nucleophilic addition
what is involved in reduction reactions of oxygen compounds?
nucleophilic addition of a hydride ion to a carbonyl. reduction is gain of electrons. increase in bonds to H or R groups, loss of bonds to oxygen or halogens
what is involved in oxidation reactions of oxygen compounds?
nucleophilic addition of oxygen to a carbon. oxidation is the loss of electrons/ electron density. increase in bonds to oxygen or halogens, loss of CH single bonds. Oxygen and halogens withdraw electron density from carbons, leaving them oxidized
what is the most common type of reaction of ketones and aldehydes on the MCAT and why?
nucleophilic addition reactions because they usually lack a good leaving group
describe the periodic trends of nucleophilicity
nucleophilicity decreases going up and to the right on the periodic table
explain how you can tell a D sugar from an L sugar
number all of the carbons in a Fischer projection, the lowest number being at the end closest to the aldehyde/ ketone. Find the highest numbered chiral carbon with an OH group. If the OH group points to the right it is a D sugar. if it points to the left it is an L sugar
differentiate between the 3 acid base theories
on the MCAT, we will most often deal with hydrogen donors and acceptors
on which side of a cell diagram is the cathode located?
on the right (reduction on the right)
what is a triglyceride?
one glycerol molecule and 3 fatty acids
what are closed systems?
only allow the exchange of energy but not mass
at constant pressure, if only PV work is done, what is the change in enthalpy?
only the heat transferred into/ out of the system
what is the name of a system where there is exchange of both mass and energy?
open system
what type of reaction occurs at the anode?
oxidation
what is it called when a element has unpaired electrons which align with an external magnetic field?
paramagnetism
what is ClO4-?
perchlorate
what would you use if you wanted to oxidize alcohols all the way to carboxylic acids?
permanganate (MnO4), chromate (CrO4) or dihromate (Cr2O7)
what is deposition?
phase change from gas to solid
what is sublimation?
phase change from solid to gas
what is PO4^3-?
phosphate
what is an important enolate in biology and with which reaction is it involved?
phosphoenolpyruvate (PEP), involved in glycolysis
what biological molecule acts much like a carbonyl?
phosphoric acid
what type of reaction if the formation of a solution?
physical reaction
what happens to bond strength when a sigma bond becomes a pi bond?
pi bonds are weaker than sigma bonds and are therefore more reactive, but since a pi bond must be added to an existing sigma bond, the overall strength of the bond holding the 2 atoms together is greater in pi bonds than sigma bonds
what is the prefix for 10^-12?
pico
what is the triple point?
point on a phase diagram where solid, liquid and gas phases exist in equilibrium
how do polar protic solvents impact nucleophiles and carbocations?
polar protic solvents are able to stabilize nucleophiles and any carbocations that may form. Stable nucleophiles DECREASE the speed of SN2 reactions, where the rate is dependent on the activity of the nucleophile and INCREASES the rate of SN1 reactions, where the stability of the carbocation is key to the rate
what is the sign on the enthalpy change in an endothermic reaction?
positive
how are the pressure and volume of a gas related to one another?
pressure and volume are inversely proportional at constant temperature as state in Boyle's law. PV=Constant
how does pressure impact solubility?
pressure has little impact on the solubility of solids and liquids, but increasing pressure does increase the solubility of gases. This is described in Henry's law which states that at constant temperature, the amount of a given gas dissolved in a given amount and type of liquid is proportional to the partial pressure of that gas in equilibrium with that liquid
what is standard ambient temperature and pressure (SATP)?
pressure of 1 atm and a temperature of 298 K (25 degrees celcius)
what type of thermal energy transfer does not require a medium?
radiation
give an example of a first order reaction
radioactive decay
what is the equation for rate law?
rate (forward)= Kf[A]^alpha[B]^beta, where Kf is the rate constant for the forward reaction, and alpha and beta are the respective reaction orders of each reactant. alpha + beta is the overall order of the reaction. If a reaction is elementary alpha and beta will be equal to the coefficients, if not, they need to be determined experimentally
what would the rate law be for a zero order reaction?
rate=k
what would the rate low be for a first order reaction?
rate=k[reactant]
what is parts per million?
ratio of the mass of the solute to the total mass of the solution multiplied by 1 million ppm= mass of solute/ total mass solution x 10^6
how do you make cyanohydrins?
react a nitrile (NC-) to a carbonyl in the presence of acid
how do you make an amide?
react an amine with a carboxylic acid or one of its derivatives. the OH group on the carboxylic acid is replaced by NH2
what is an isovolumetric process?
reaction where the volume remains the same
how can you use the values of Q and K to determine in which direction the reaction will shift?
reactions always move towards equilibrium, so at any point in a reaction, the value of Q will be changing to get closer to K. If Q is equal to K, the reaction is a t equilibrium. If Q is greater than K, the ratio of concentration of products to reactants is greater than at equilibrium, so the reaction will shift to the left (increase the concentration of reactants, and decrease the ratio). When this happens, the rate of the reverse reaction will be greater than the rate of the forward reaction. If Q is less than K, the ration of concentration of reactants to products is less than at equilibrium, so the reaction will shift to the right to increase product concentration and decrease reactants
what type of reaction occurs at the cathode?
reduction
explain the direction of electron flow in a galvanic cell
reduction (gain of electrons) occurs at the cathode and oxidation (loss of electrons) occurs at the anode. Electrons flow from the source of electrons (anode) to the recipient of said electrons (the cathode). This is opposite of the direction of current, which for some reason is the reverse of electron flow, so current travels from the cathode to the anode
why does adding H or R groups result in reduction of the carbon?
reduction is the gain of electron density. R groups and H+ push electron density towards the carbon, increasing its electron density
how does the internal energy of a gas change during expansion of a balloon?
refer to the equation delta E= q+w. If the process is adiabatic, there is no heat transfer, so q=0 and delta E is entirely dependent on the work done. As the gas expands, it is doing work on the surroundings so work and change in energy will be negative ie the internal energy of the gas decreases. The temperature of a gas is related to its internal energy, so it will also decrease. Pressure must also decrease since volume has increased
how do you name amides?
replace the ic in the corresponding acid with amide ie acetic acid becomes acetamide
what is the SI unit for time?
s
what is a structural isomer?
same molecular formula but different bond connectivity
what type of biological molecule is able to store the most energy and has the highest heat of combustion?
saturated fat. fats have about twice the energy storage capacity of sugars and proteins
compare the melting points of saturates and unsaturated fatty acids. why is this the case?
saturated fatty acids have higher melting points than non-saturate fatty acids because they stack and solidify more easily. In saturated acids, there are no double bonds, so the acids are straight and they stack nicely together, allowing them to solidify more easily, whereas the double bonds in unsaturated fatty acids cause kinks and they don't solidify as well
if K>1 what is the value of delta G naught?
smaller than 1
describe the physical characteristics of alkali metals
soft metallic solids with low densities and low melting points
in an SN1 reaction, upon what is the rate dependant?
solely on the concentration of the substrate (the electrophile which is also the carbocation)
explain what is happening in a galvanic cell where Zn is the anode and Cu is the cathode (this involved a salt bridge).
solid zinc atoms are good reducing agents, so they want to get rid of their electrons, but they need somewhere to send them. Cu2+ ions in solution would like to accept the electrons, but there needs to be a path for them to get there. The copper wire allows the electrons to travel from the zinc to the copper, but without the salt bridge, the current wouldnt flow because a charge difference would build up and building a charge difference costs energy. The salt bridge allows ions to flow (anions towards the zinc anode and cations towards the copper cathode) and carry away any charge difference that might build up.
what is the difference between solubility and solubility product?
solubility product is an expression of equilibrium. When a solid dissolves, the solubility product (Ksp) only includes products. The solubility is a constant that can be looked up and is fixed for a given temperature. Solubility is the maximum number of moles of a solute that can dissolve in solution and depends on both temperature and ions in the solution
what are the important exceptions to Le Chatelier's principle?
solvation reactions and reactions where the pressure was changed by adding a non-reactive gas .
how do acids taste?
sour or tart
what is the shape of s orbitals?
spherical
how do you name esters?
start with the name of the alcohol, change the ending from ol to yl and add the name of the carboxylic acid as its carboxylate salt. Example: ethanol and acetic acid gives ethyl acetate
what are the state functions?
state functions are pathway independent and describe the current state of a system. If you know 3 state functions (one of which must be extrinsic), then you can extrapolate all the other state functions for that material/ state 1. internal energy (U) 2. temperature (T) 3. pressure (P) 4. volume (V) 5. enthalpy (H) 6. entropy (S) 7. gibbs energy (G)
what do you call properties that describe the current state of a system?
state functions. these do NOT depend on the path taken to reach the state. only the present is relevant
what do you call two unique molecules with the same molecular formula and the same connectivity?
stereoisomers
what is the difference btw strong and weak acids and bases?
strong acids and bases dissociate completely in aqueous solution, whereas weak acids and bases do not go to completion
what determines whether and acid will be weak or strong
strong acids are easily able to give up their H ions, whereas weak acids hold them more tightly. there are 3 general factors to consider. 1. the strength of bond holding the hydrogen to the molecule. the stronger the bond, the less likely the acid will deprotonate 2. the polarity of the bond (polar bonds pull electron density away from hydrogens) 3. the stability of the conjugate base. if the base that is formed would be strong/ a stronger base than the acid, the reaction is unfavourable. you want to go from strength (reactivity/ instability) to stability
how do titrations differ if the solution being titrated is a strong or weak acid?
strong acids can be considered to be completely deprotonated in aqueous solution, however the degree of deprotonation of weak acids will depend on the pH of the solution. If a weak acid like acetic acid is in a strongly basic solution, virtually all of the acetic acid will deprotonate and it will be found in the solution as its conjugate base. In contrast, if it is in a solution of pH=1, virtually non of the acetic acid will be able to deprotonate ,and it will be found in solution as acetic acid. . The intrinsic pKa of acetic acid remains the same, but the environmental pH determines the behaviour of the acid in solution.
describe electron withdrawing groups
strongly electronegative and pull electron density away from the rest of the molecule
what type of isomer has the same molecular formula but different bond connectivity?
structural isomers
what is the name of the phase change from solid to gas?
sublimation
what is SO4^2-?
sulfate
what is SO3^2-?
sulfite
what is the element most commonly found with an expanded octet?
sulfur
if i wanted to make a carboxylic acid from a ketone, how would I do it?
take a carbonyl and react it with a nitrile in the presence of acid to make a cyanohydrin. then add acid and water and the cyanohydrin will become a carboxylic acid
what is the only factor that will change the partial pressure equilibria constant of a reaction?
temperature
what is the critical temperature?
temperature above which a substance cannot be liquefied regardless of how much pressure is exerted
what is emissivity?
that fraction of radiation that is absorbed by a surface. it is a value between 0 and 1 and higher emissivity means that more radiation is absorbed
which is greater, the 1st or 2nd ionization energies and why?
the 2nd is greater. Once you have removed the first electron, there is more positive attractive force acting on the electrons, which means they are held more tightly by the nucleus. This is another way of saying that removing an electron reduces shielding and increases the Zeff of the remaining electrons
what is the bond that humans and most animals are unable to break in cellulose?
the B 1-4 linkage
how does the second proton released by a polyprotic acid affect the acidity of the solution?
the acid is usually so weak as to be negligible. the second proton from H2SO4 is not weak, but except in dilute concentrations (less than 1 M) it has a negligible effect on the acidity of the solution
how does the formal charge of an atom in a molecule relate to the actual charge of the whole molecule?
the actual charge of the molecule is the sum of the formal charges of the constituent atoms
how do resonance structures relate to the actual molecule?
the actual molecule is represented by the weighted average of all resonance structures for that molecule
what is heat capacity?
the added energy required to increase the temperature of a given substance by 1K or 1C (this will be the same since the scale size is the same). Conversely it can be the energy that must be lost to reduce the temperature of the substance by 1K/ 1C
how does keto enol tautomerization occur?
the alpha carbon is deprotonated and the carbonyl oxygen is protonated. these forms exist in equilibrium, though usually the reaction favours the keto product. these are NOT resonance structures
how is an amide bond formed in proteins?
the amino group on one end of an amino acid acts as a nucleophile to attack the carbonyl carbon of the carboxylic acid on another amino acid, leaving OH- as the leaving group
what is the effective nuclear charge?
the amount of charge felt by the most recently added electron. this will differ from the actual charge of the nucleus due to the presence of other electrons which 'shield' the new electron
what is partial pressure?
the amount of pressure contributed by a single gas in a gaseous mixture. The partial pressure of a particular gas is the total pressure of the gaseous mixture multiplied by the mole fraction of the particular gas
how is the atom described in the Bohr theory?
the atom is a nucleus surrounded by electrons in discrete electron shells
what is saponification?
the base catalyzed breakdown of triglycerides into glycerol and fatty acids
what is beta decay?
the breakdown of a neutron into a proton and electron and the expulsion of the newly created electron
what is electron capture?
the capture of an electron and the merging of the electron and a proton to create a neutron
the phosphate group in nucleic acids behaves similarly to which other reactive group?
the carbonyl group, because PO double bonds are similar in activity to CO double bonds
what is the strange step in the Gabriel synthesis of amino acids?
the central carbon loses a hydrogen and becomes a carbanion, which then acts as a nucleophile
what is a standard enthalpy of formation? (delta Hf)
the change in enthalpy for a reaction that creates one mole of that compound from its raw elements in their standard states
what is an emission line spectrum?
the characteristic spectrum of energy that is released when electrons of a specific element fall from an excited energy state to a lower energy state
what is internal energy?
the collective energy of molecules measure on a microscopic scale, including rotational, vibrational, translational, electronic, intermolecular and rest mass energies. it does NOT include bond enthalpies or the macroscpic mechanical energies like motion or position of the system as a whole
what happens when the pH is greater than the pKa of a compound?
the compound will interpret the environment as aprotic (few H+ ions) and is more likely to behave acidic (give up its own H+)
what happens when the pH of a solution is lower than the pKa of an compound?
the compound will interpret the environment as protic (full of H+) and it is less likely to act acidic (ie give up its H)
what does it mean when a reactant has a zero order in the rate law?
the concentration of that reactant does not impact the rate of reaction
what does the rate depend on in an SN2 reaction?
the concentrations of both the nucleophile and the substrate
what is the equation to determine the equilibrium constant (K)? what exceptions do you need to keep in mind?
the concentrations of pure liquids and pure solids do not change over the course of a reaction, though their amounts can. Pure solids and liquids are represented in this equation with a value of 1
what is chemical equilibrium?
the condition when the rate of the forward reaction equals the rate of the reverse reaction. at equilibrium, there is no net change is the concentrations of the products or reactants
how do you determine which resonance structures contribute more or less to the actual structure of the molecule?
the contribution made to the structure of the actual molecule is roughly proportional to the structure's stability. the most stable structure makes the greatest contribution and vice versa
what is the rate determining step in an SN1 reaction?
the creation of the carbocation (electrophile)
how does the percent dissociation respond to increased acidity of the solution?
the dissociation decreases as the solution acidity increases. this means acids dissociate less, but does not indicate that the solutions are less acidic. Acid dissociation decreases with acid concentration, but acid strength increases with acid concentration
what point has been reached in a titration when the indicator changes colour?
the end point has been reached. This is NOT necessarily the equivalence point, since indicators act over a range of values. An indicator whose range overlaps the equivalence point will be chosen
what is ionization energy?
the energy required to detach an electron from an atom
what is the heat of fusion?
the enthalpy associated with melting
what is heat of vaporization?
the enthalpy associated with vaporization
how would you calculate heat of solution (delta H sol)?
the enthalpy change of a reaction in a closed system at constant pressure equals the heat (delta H=q). On the MCAT, this will apply to solution problems. So delta Hsol= delta H1+ delta H2 + delta H3 ....
what is the difference between zero point enthalpy and zero point entropy?
the enthalpy scale was created relative to common chemical reactions and enthalpy isn't a real property, whereas zero point entropy is based on an absolute scale rather than a silly made up relative scale
briefly define the second lat of thermodynamics
the entropy of an isolated system will never decrease. The overall disorder of the universe is increasing
what determines the spontaneity of a reaction when delta S and delta G have the same signs in the gibbs free energy equation?
the equation in question is G=H-TS, the negative sign indicates that the sign of entropy will be flipped. When you are given H and S values with the same sign, S will actually count against H and manipulating the temperature will tip the reaction in either direction (towards positive G or negative G)
what is Kw?
the equilibrium constant for the autoionization of water
what is the point of greatest universal entropy in a reaction?
the equilibrium point
what is the isoelectric point (pI) for uncharged amino acids?
the first equivalence point, it can be calculated as the average of the 2 pKas. The pI of all uncharged AAs will be close to 6 but will differ slightly for each
what happens when the critical point is surpassed on a phase diagram?
the fluid becomes a supercritical fluid and will have the properties of both a liquid and a solid
what is the electrostatic force?
the force between charged objects
what is a reference form?
the form of the substance that is the most stable at 1 bar and a chosen temperature. for a pure gas, the reference form must act as an ideal gas
what reagent, used to make alcohols, is too potent a base to exist on its own?
the hydride ion (H-). it has to be hidden in hydride reagents such as LiAlH4 or NaBH4
what happens when you protonate an alcohol with an haloacid?
the hydrogen from the alkyl halide protonates the OH group and then the halide ion attacks the electrophile and water leaves. now you have an alkyl halide
what is aromaticity?
the increased stability of a cyclic molecule due to electron delocalization (resonance)
describe the differences between the kelvin and celcius systems
the interval between values is the same for both but celcius is a relative scale, whereas kelvin is absolute. In practice that means that you can't say that 10 C is half as hot as 20 C, but you CAN say that 100K is half as hot (half as much energy) as 200K
which is more stable at room temperature, the keto or enol tautomer? why?
the keto tautomer is more stable because the double bond is weakened by the electronegativity of the oxygen
contrast the kinetic and thermodynamic enolates
the kinetic enolate is the less substituted enolate. it is made when one of the 3 possible acidic alpha hydrogens is removed. this occurs quickly and is kinetically favored. the thermodynamic enolate is on the more substituted carbon. it is more difficult to produce because it take greater activation energy, but the product is more stable, so it is thermodynamically favoured
low temperatures usually drive reactions towards which type of product and why?
the kinetic product. The kinetic product has a lower activation energy, so it is more likely to form than the thermodynamic product when the energy of the system is lower
what causes lactose intolerance?
the lack of the enzyme that breaks the B1-4 galactosidic linkage in galactose
how do the values of Ka, and pKa relate to the strength of the acid?
the larger the Ka (the products over reactants, so the reaction progress), the smaller the pKa, the stronger the acid. a Ka greater than 1 and a pKa less than zero indicate a strong acid
what is the most general definition of acids and bases?
the lewis theory. It defines and acid as any substance that accepts a pair of electrons and a base as any substance that donates a pair of electrons
what is the special characteristic of water on its phase diagram?
the line between liquid and solid has a negative slope, indicating that ice must be less dense than water
what happens when the vapor pressure of a liquid equals the atmospheric pressure?
the liquid will boil. A liquid can be brought to a boil either by raising its temperature, thereby raising its vapor pressure until it reaches the atmospheric pressure, or by decreasing the atmospheric pressure until it equals the vapor pressure, or both.
what indicates standard state conditions?
the little circle naught symbol
why are amides the least reactive carboxylic acid derivative?
the lone pair on N donates electron density to the carbonyl carbon, stabilizing it
what is alpha decay?
the loss of an alpha particle (a helium nucleus containing 2 protons and 2 neutrons)
what type of bonds hold the glucose molecules together in amylopectin?
the main chain of glucose is formed by alpha 1-4 linkages and the branches are made from alpha 1-6 linkages
what is the law of mass action?
the mathematical relationship between a chemical equation and the associated equilibrium constant. The equilibrium value (K) that comes out of the relationship is unitless, because it is approximating another unitless quantity called activity (K). K will only change for a given reaction if the temperature is changed
on what scale doe the second law of thermodynamics not apply?
the microscopic scale, because thermodynamics relies on macroscopic properties and the statistical power of many molecules. this breaks down at the microscopic level
what is the difference observed when mixing heterogeneous substances in liquid rather than gaseous form?
the molecules in a liquid exert much stronger intermolecular forces against/ towards each other than do gases, so they are more impacted by things like polarity differences. When you mix different gases, the mixture will always be homogeneous, because the molecules are spread so far apart that they dont repel each other or attract each other the way liquids to. Conversely, if you mix liquid water and gasoline, they are unable to mix because liquids are subject to much stronger attractive and repulsive forces
how does the electrical potential of a reaction relate to its reaction progress?
the more positive the reaction potential ,the more likely the reaction is to proceed
how do you find the cell potential for a concentration cell?
the nernst equation. by its definition, the concentrations of a concentration cell CANNOT be 1M, otherwise the cell potential would be zero
describe nucleophiilic addition to aldehydes/ ketones under BASIC conditions
the nucleophile attacks the carbonyl carbon and forms a tetrahedral intermediate, with the electrons from the bonds going to the oxygen. the negatively charged oxygen then abstracts a proton from a water molecule (or another mild proton source) , the product is an alcohol
what is molecularity?
the number of molecules that need to collide simultaneously for a reaction to occur
what is the mole fraction?
the number of moles in a given substance in a mixture divided by the total number of moles in that mixture
how do you find the concentration of the conjugate base at the equivalence point?
the number of moles of acid divided by the volume of the acid solution PLUS the volume of the base used to titrate. DO NOT forget the volume of the base. The concentration of the conjugate base will NOT be the same as the original acid since the volume has increased, but the amount of acid has not
what is indicated by the atomic number (Z)?
the number of protons. atoms of a specific element can have a variable number of neutrons (isotopes) and electrons (ions), but must have their specific number of protons
what is the carbon at the end of the fatty acid chain called?
the omega carbon
how do the oxidation states of atoms relate to the actual charge on the molecule?
the oxidation states of the individual atoms must add up to the actual charge on the molecule/ ion
what is the pH of a titrated weak acid strong base solution at the half equivalence point?
the pKa of the acid. at this point 50% of the acid is protonated and 50% is deprotonated, which is exactly what occurs at pKa.
what is the system?
the part of the universe being studied
describe the reaction used to bind chains of nucleotides together with phosphodiester bonds
the phosphate acts like a carbonyl group, so the oxygen attached to the 3' carbon of one nucleotide attacks the phosphate attached to the 5' carbon of the other nucleotide. a hyroxyl (or water depending on the conditions) acts as the leaving group, making the reaction a nucleophilic substitution reaction.
what is the critical point?
the point on a phase diagram where the critical pressure and temperature meet. Fluids beyond this critical point will have the characteristics of both a liquid and a solid and are called super critical fluids
what is the cell potential in a galvanic cell?
the potential difference between the terminals when they are not connected. Connecting the terminals decreases the potential and the drop increases as the current increases
what is designated by the 3rd quantum number 'Ml'?
the precise orbital within the subshell. each orbital can contain 2 electrons and each subshell has a different number of orbitals within it. values for Ml range from -l to +l.
what does a chemical formula written above the reaction arrow indicate?
the presence of a catalyst
what is the critical pressure?
the pressure required to achieve the liquid phase when the substance it at its critical temperature
in an first order reaction, how are the rate and concentration of reactants linked?
the rate is directly proportional to the concentration of a single reactant
in a zero order reaction, what is the relationship between the rate and the concentration of reactants?
the rate it completely independent of the concentrations of any reactant is super saturated enzyme reaction
explain how the rate law is determined for multi step reactions/
the rate of a reaction is determined by the slowest step. If the first step is the slowest step, then that step alone determined the rate of the reaction. If a later step is the slowest, it is still the rate determining step, but any other steps that came before will also contribute to the rate law. Any steps that come AFTER the rate determining step will NOT contribute to the rate law
what would happen to your SN2 reaction of you used a polar aprotic solvent?
the rate would increase
what happens at a solutions saturation point?
the rates of dissolution of the solute into solution and the precipitation of the solute out of solution are at equilibrium
what is mass percentage in solution chemistry?
the ratio of the mass of the solute to the total mass of the solution, multiplied by 100. mass %= mass of solute/ total mass of solution x 100
which half reaction drives the reaction in redox?
the reaction that is more likely to be reduced will drive the reaction and will get its electrons from the reaction with which it is coupled, which becomes an oxidation reaction
how is the pressure of a real gas related to the pressure of the same ideal gas?
the real pressure exerted by a gas on its container will always be less than for an ideal gas for 2 reasons. Ideal gases are considered to have perfectly elastic collisions with each other and also to exert absolutely no forces on each other, whether attractive or repulsive. both of these increase the energy of the gas molecules when they impact the container (real gases actually exert attractive forces that slow the molecules before they impact), so the real pressure is necessarily lower than ideal pressure
what is the equilibrium equation for gaseous reactions?
the result is the partial pressure equilibrium constant
why are alkali earth metals more stable than alkali metals?
the second electron in their s orbital makes them less reactive (s orbital is full)
what is designated by the principal quantum number 'n'?
the shell level of the electron, with low numbers closest to the nucleus. it corresponds roughly to the energy level of the electrons within that shell
what is tautomerization?
the shift from a carbonyl (keto) tautomer to an alkene with an alcohol (enol) tautomer.
describe the acidity trends of lewis cation acids
the smaller the cation and the higher the charge, the more electrophilic in nature and the stronger the acid. alkali and heavier alkaline earth metals are not included
what is an empirical formula?
the smallest whole number ratio that can be used to represent the proportions. all ionic compounds are represented by their empirical formula
why do solvation reactions not obey the trends of Le Chatelier's principle?
the solubility of a salt generally increases with rising temperature, even when the reaction is exothermic and would be predicted by Le Chatelier to proceed in the other direction. This is due to the significant entropy increase that occurs when substances dissolve. The entropy in this case becomes more important than the temperature
what do you call the equilibrium constant for a solvation reaction?
the solubility product Ksp. Remember that pure solids and liquids have a mole fraction of 1 and will be left out of the equilibrium expression
what happens when you add a non-volatile solute to a liquid?
the solute molecules will spread out and some will take up surface area on the surface of the solution. Since they take up surface area, but do not break free into the gas phase, the non-volatile solute actually decreases the number of molecules which can break free of the solution. This decreases the vapor pressure of the solution compared to the pure solvent.
the rate constant in liquids is a function of what 2 factors?
the solvent and the temperature. Solvents decrease the rate of reaction for 2 reasons. 1. the degree of solvation impacts the rate of reaction because the reactant molecules get pulled apart from each other and surrounded by solvent molecules. The interactions btw solvent and reactant can help to stabilize reactants and even intermediates, which decreases the rate of reaction. 2. the viscosity of the solvent also impacts the rate of reaction. the cage effect means that molecules of reactant gets trapped inside cages of solvent molecules, and bounce around very quickly inside their cages until they are able to escape into another cage of solvent. If there is only 1 reactant molecule in a cage, it is impossible for that reactant to react until it escapes to a cage that also includes a reactant. The result is that reactant in a solvated liquid collide at approximately the same rate as collisions between gas molecules of the same concentration Increasing temperature will increase the rate of collisions and therefore the reaction rate. in liquid reactions
what is designated by the 4th quantum number 'Ms'?
the spin of the electron. values are +1/2 and -1/2. this number distinguishes between the 2 electrons in a given orbital
how does the concentration used in the solutions of the galvanic cell impact how you determine the cell potential?
the standard conditions call for 1M concentrations of liquid. At 1M, the reduction potentials can be determined from a table. When concentrations other than 1M were used, you need to use the Nernst equation to get your potentials
which type of amino acid synthesis gets you a racemic mixture of products?
the strecker synthesis
what are 2 ways to synthesize amino acids de novo?
the strecker synthesis and the gabriel synthesis
what holds the nucleus of an atom together?
the strong nuclear force
what is the broad definition of thermodynamics?
the study of energy and how it relates to macroscopic properties of chemical systems. They rely of statistics and can only be applied to large systems of many molecules, not single molecular collisions etc
what is kinetics?
the study of reaction rates and how rapidly a reaction occurs and the factors that impact the speed of a reaction
what is designated by the second quantum number 'l'?
the subshell. s=0, p=1, d=2 and f=3
what are the differences between cis and trans geometric isomers?
the substituents in cis isomers are on the same side of the bond, whereas in trans isomers they are on opposite sides of the bond. cis isomers have a dipole moment but trans do NOT. Because of their dipole moment, cis isomers have stronger intermolecular forces than trans isomers and therefore have higher boiling points. However, due to their substituents being on the same side, cis molecules do not form crystals as well as trans isomers and so they have lower boiling points than trans isomers. Cis isomers are also less stable than trans isomers, because their substituents are crowded on the same side, leading to steric hindrance and higher energy levels
what is Hess' law of heat summation?
the sum of the enthalpy changes for each step is equal to the total enthalpy change regardless of the path chosen
what is electronegativity?
the tendency of an atoms to attract electrons shared in a covalent bond
what is Dalton's law?
the total pressure exerted by a gaseous mixture is the sum of the partial pressure of each of its gases
the temperature of a gas or liquid is directly proportional to what?
the translational kinetic energy of its molecules
what do you call the speed at which a catalyst works?
the turnover number
what is reduction synthesis?
the use of hydrides to synthesize alcohols
how are volume and temperature of a gas related to one another?
the volume of a gas is directly proportional to its temperature at constant pressure as stated in Charles' law: V/T= constant
to what does the V in the ideal gas la PV=nRT refer?
the volume of the container in which the gas is constrained. Ideal gases have zero molecular volume, so the volume in the equation cannot apply to the container itself
what is electron affinity?
the willingness of an atom to accept an additional electron. Also described as the energy released when an electron is added to an isolated atom
what occurs at the equivalence point of a titration?
there are equivalent moles of acid and base in solution. WARNING: this does NOT mean that the equivalence point will be at neutral pH. If the acid and base are of comparable strength, the equivalence point will be neutral, but if a weak acid was titrated with a strong base, the equivalence point will be above 7, and if the acid is stronger than the base, the equivalence point will be below 7
what is required for there to be vibrational energy?
there must be covalent bonds around which to vibrate. atoms in a monoatomic gas have no vibrational energy
in what state will an acid or base be found when pH=Pka or pKb?
there will be a 50/50 mixture between the acid and its conjugate base or the base and its conjugate acid. the further you move away from the pKa/ pKb, the greater the ratio will become. For acids, the further below the pKa you go, the less deprotonated it will be, so you will find more acid and less conjugate base. The more you go above its pKa, the more you will find it has give up its H and youll get more conjugate base than acid. the same is true in reverse for bases
what is radiation?
thermal energy transfer via electromagnetic waves. radiation does NOT require a medium
what is convection?
thermal energy transfer via fluid (liquid or gas) movements. Differences in pressure and density drive warmer fluid in the direction of cooler fluid
what is conduction?
thermal energy transfer via molecular collisions and requires direct physical contact. An object's ability to conduct heat is called its thermal conductivity (k) and is dependent on its composition and to a much lesser degree, on its temperature
high temperatures usually drive a reaction towards which type of product and why?
thermodynamic product. the heat helps over come the higher AE for the thermodynamic product to be formed
explain the struggle between competing thermodynamic and kinetic reactions
thermodynamic reactions have higher activation energies but they produce more stable products, whereas kinetic reactions have lower activation energy but produce less stable products
what are conformational isomers?
these are not true isomers. they are different spatial representations of the same molecule due to spinning around a single bond. eclipsed, staggered and gauche are examples of these
in a second or third order reaction, how are the rate and concentration of reactants linked??
these come in 2 types. either 1. the rate is proportional to a single reactant raised to the second or third power or 2. the reaction rate is proportional to the product of the concentrations of multiple reactants
what are diasteriomers?
they are a type of stereoisomer. diasteriomers have the same molecular formula and bond connectivity but are NOT mirror images of each other and are NOT the same compound. Diasteriomers with multiple chiral centers will have the same absolute configuration at at least one chiral center
describe the polarity of fatty acids
they are amphipathic, meaning they have both a hydrophobic (carbon tail) and a hydrophilic (carboxylic acid) end. The carbon tail predominates and so the molecule is non-polar
why does adding oxygen or halogen result in oxidation of the carbon?
they are both highly electronegative, and thus they pull electron density from the carbon, lowering its oxidation state
how can you tell cellulose and amylose apart?
they are both long straight chain of glucose molecules, but cellulose uses beta 1-4 linkages, whereas amylose uses alpha 1-4 linkages. humans and most animals are unable to digest the beta linkages in cellulose
carbohydrates that have the same structure except for the configuration of a single chiral carbon are known as what?
they are epimers, or stereoisomers of each other
describe the physical properties of alkaline earth metals
they are harder, more dense and melt at higher temperatures than alkali metals
what type of property are reduction potentials?
they are intensive properties. you DO NOT have to multiply the reduction potential by the number of times that it occurs
what is a common function of acetals and ketals?
they are not easily returned to their original form, since the OR bond is difficult to break and return to a CO double bond. this makes them ideal PROTECTING GROUPS to prevent aldehydes or ketones from reacting at the carbonyl carbon
what are polar aprotic solvents and what do they do?
they are polar solvents that DO NOT hydrogen bond, so they do not form strong bonds with ions. they increase the rate of SN2 reactions and decrease the rate of SN1 reactions
how can you tell the difference between glycogen and amylopectin?
they both use the same types of linkages (alpha 1-4 for the chain and alpha 1-6 for the branches )and are made completely of glucose, but glycogen is much more highly branched than amylopectin
what is special about amides compared to other carboxylic acid derivatives?
they can act as weak acid or weak bases
what are the 2 ways a catalyst can increase the rate of reaction?
they can reduce the activation energy, meaning more collisions will have sufficient energy to react successfully, or they can increase p, the steric factor from the Arrhenius equation, which increases the number of successful collisions
what happens when you heat phosphoric acids?
they form phosphoric anhydrides
why do phosphoric acids behave much like carbonyls?
they have a polar PO double bonds, much like the polar CO bond in carbonyls. the difference is that P has empty D orbitals, which can be used to make more than 4 bonds
how do catalysts impact the rate of reactions?
they increase the rate of reactions by reducing the Ea of the reaction, making it easier for the reaction to proceed
how do R and S configurations differ other than the fact that they are chiral?
they rotate a plane of polarized light to the same degree but in opposite directions. the R or S designation does NOT indicate which direction the molecule will rotate the light. that must be determined experimentally
thermodynamic functions work only on what scale? why?
they work on the macroscopic scale and cannot be applied to the microscopic level because they rely on the averages of large numbers of molecules. The microscopic level can only be applied to thermodynamic functions by statistics
what is significant about the half equivalence point on a titration curve?
this is the point where the curve is the flattest and the concentration of the acid and its conjugate base are equal. In this range, you can add the highest concentration of acid/ base and get the least pH change. A solution at the half equivalence point is considered to be buffered
what is molality used for?
to calculate freezing point depression and boiling point elevation
what is a calorimeter used for?
to determine the energy change associated with a chemical or physical reaction. This is reliant upon the relationship between heat transfer and temperature change
if the temperature of a reaction is changed, how does that impact the equilibrium of that reaction?
to find out, write heat as a reagent or product, depending on the type of reaction. If heat was removed, the reaction moves towards the side that has heat, if heat was added, the reaction moves away from the side that has heat
what is the common function of anhydrides in synthesis?
to make esters and amides
mmHg is equivalent to which other measurement of pressure?
torr
which direction do positive ions travel in e galvanic cell?
towards the cathode. The whole point of the salt bridge is that it balances charge, so as the electrons flow towards the cathode, negative charge would build up if there wasnt a corresponding flow of positive charge to the cathode
which has a higher melting point, cis or trans isomers, and why?
trans isomers. they more readily create crystals than cis isomers, since their substituents are not concentrated on one side. this leads to a higher melting point than cis isomers
what is it called when you react an alcohol with an ester and what happens?
transesterification. you change the type of ester by replacing the old acid with the new one. Yield is not very good, but you can improve it by taking advantage of Le Chateliers' principle
what is the difference between an intermediate and a transition state?
transition states only exist for a fleeting moment of time, whereas intermediates exist for longer, can be isolated and are at lower energy than their associated transition states. On a reaction progress graph, a reaction with an intermediate / intermediates would show multiple peaks and troughs between reactants and products. The peaks would be the higher energy transition states where bonds are breaking and forming and the troughs would be the intermediates
what is the sole contributor to kinetic energy in monoatomic gases?
translational energy
what is the only component of internal energy that can change in an ideal gas? what happens when it changes?
translational energy. Any change in translational will lead to a corresponding change in temperature
what is maltose?
two glucose molecules held together by alpha 1-4 glycosidic linkages
what is relative configuration?
two molecules have the same relative configuration if they differ in only 1 substituent around their chiral carbon and all other substituents are oriented in the same way
what is the zeroth law of thermodynamics?
two systems in thermal equilibrium with a third system are in thermal equilibrium with each other. therefore, two systems in thermal equilibrium with each other share a thermodynamic property: temperature. Basically it says that temperature exists, and the first and second laws of thermodynamics are dependent on the existence of temperature
how do you prevent a nucleophile from acting like a base?
use a less bulky nucleophile
how can you preserve the alkoxy group in an ester when it undergoes other reactions (ie prevent transesterification from occurring)?
use the alcohol that is already present in the ester as the solvent
what is the Nernst equation and what is it used for?
used when the concentrations are not 1M
what is the name of the phase change from liquid to gas?
vaporization
describe how Fischer projections represent molecules
vertical lines are assumed to be oriented into the page. horizontal lines are assumed to be oriented out of the page. they are usually used for representing carbohydrates and are an easy way of showing the 3D shape
what component of internal energy is responsible for protein denaturation at high temperatures?why?
vibrational energy. as a system heats up, the molecules vibrate more quickly and they gain sufficient energy to overcome the energetic barriers of the intermolecular forces that hold them together
what happens when you add a volatile solute to a liquid?
volatile solutes have a vapor pressure. As the molecules of solute spread out, they will compete with the molecules of liquid for the surface area. Unlike with non-volatile solutes, the some molecules of volatile solutes will escape the liquid phase, as will some molecules of the liquid, and both will contribute to the vapor pressure. As in any solution, the new vapor pressure will be different than for pure compounds. The sun of the partial vapor pressures will equal the total vapor pressure of the solution, so you use a modified version of Raoult's law: Pv=XaPa+ XbPb where Pv is the vapor pressure of the solution, Xa and Xb are the mole fractions of the respective compounds and Pa and Pb are the vapor pressures of the pure compounds. Think of it this way: if 97% of a solution is solvent, then the vapor pressure of the solution will be 97% of the vapor pressure of the pure solvent PLUS 3% of the vapor pressure of the pure solute
how are volume of an ideal gas and number of moles related?
volume of a gas is proportional to the number of moles as stated in Avogadro's law: V/n= constant
how do you calculate PV work in a system with constant pressure?
w= -P delta V. the work is negative because the system is doing work on its surroundings, and so the system is losing energy to its surroundings OR w= area under the graph of the PV diagram
what is the by product of the formation of lactones?
water. it is a dehydration reaction between an alcohol and a carboxylic acid on the same carbon chain and a water molecule is lost
how do you determine what is the solute and what is the solvent in a solution?
whatever compound there is more of is the solvent, whatever there is less of is the solute
compare the general trends in heat capacity between larger and smaller molecules. why does this occur?
when a molecule/ substance absorbs energy, not all of the energy goes towards raising the temperature. Some energy is offset into individual atoms as they increase their kinetic energy and stretch their intramolecular bonds. The more bonds a molecule has, the more energy can be diverted from raising the temperature, so larger molecules will tend to have higher heat capacities than smaller molecules, where more of the energy will contribute to increasing the temperature
how is an anomer made?
when a ring closure occurs in a cyclic diastereomer at the epimeric carbon
what is solvation?
when ionic compounds dissolve, the cations and anions are broken apart and are surrounded by the oppositely charged ends of the polar solvent. in water, this process is called hydration. The number of water molecules required to solvate a solute varies, but is usually 4 or 6
when does a phone battery act as an electrolytic cell?
when it is charging (this makes sense since electrolytic cells require energy input)
when does a phone battery act as a galvanic cell?
when its in use (this makes sense since galvanic cells react spontaneously)
when does a sigma bond form?
when the electrons are localized in the space between the 2 atoms
what is solvolysis?
when the solvent acts as the nuceophile
when do real gases deviate from ideal behaviour?
when their molecules are close together, such as at high pressures (>10 atm)and low temperatures (near the compound's boiling point). Under these conditions, the volume of the molecules themselves becomes significant and can no longer be presumed to be zero. the real volume of a gas will always exceed the volume found using the ideal gas equation and the real pressure exerted by a real gas will be less than the pressure given in PV=nRT
describe how work is done differently than heat at the miscroscopic level
when work is done, energy is transferred by ordered molecular collisions with a net force direction ie upwards if an object was lifted. energy transfer as heat occurs through random collisions between high and low energy particles. directional collisions are the defining difference btw work and heat on the molecular scale
do solids have a vapor pressure?
yes. the melting point is the point at which the vapor pressure of the solid phase is equal to the vapor pressure of the liquid phase. above the melting point, the vapor pressure of the liquid is greater than the vapor pressure of the solid, and below that temperature, the reverse is true
what is the heisenberg uncertainty principle?
you cannot know both the position of a particle and its momentum simultaneously. Measuring one inherently adds uncertainty to the measurement of the other. this is due to wave/ particle duality of matter
how can you predict the pH of a salt solution?
you compare the conjugates of the respective ions. The conjugate of the cation will be either what is left after you remove a proton or if thats not possible, what is left when you add OH. For example Na+ would have NaOH as its conjugate, but NH4 would have NH3 as its conjugate. The conjugate of the anion results from the addition of a proton, so for Cl- it would be HCl and for NO3 it would be HNO3. If you dissolve NaCl in water, you get Na+ and Cl-, whose conjugates would be NaOH and HCl, both strong, so the salt is neutral. If you dissolve NH4NO3, the conjugates will be NH3 and HNO3. NH3 is neutral, but HNO3 is a strong acid, so the salt will be weakly acidic
what happens when you react an aldehyde or ketone with an alcohol?
you get a hemiacetal/ hemiketal respectively
what is formed when an amine attacks an aldehyde or a ketone?
you get imines (aldehydes) and enamines (ketones)
what assumption must be made when dealing with polyprotic titrations?
you have to assume that the 1st proton completely dissociates before the second proton begins to dissociate
how do you differentiate between compounds with double bonds that have more than 2 substituents?
you use the E/ Z naming system. if the highest priority substituents are on the same side, they are Z (zusammen) and if they are on opposite sides they are E (entgegen)
what order would a en enzymatic reaction be if the concentration of substrate was way more than the concentration of enzyme?
zero order. once all the enzymatic active sites are filled, adding more substrate can have no effect on the rate of reaction