Gen Chem/Orgo
Neutralization
A reaction of an acid with a base, yielding a solution that is not as acidic or basic as the starting solutions were. - A type of double-replacement reaction - Acid + base --> salt + H2O HCl (aq) + NaOH (aq) --> NaCl (aq) + H2O (l)
Coordinate Covalent Bonds
A single atom provides both bonding electrons. Most often found in Lewis acid-base chemistry
Radioactive Decay
A spontaneous process in which unstable nuclei lose energy by emitting radiation
closed system
A system in which no matter is allowed to enter or leave - Can exchange energy but not matter with the environment
Isolated System
A system that can exchange neither energy nor matter with its surroundings. Exchange neither matter nor energy with the environment
Glycosidation
Addition of a sugar to another compound
Rate Law
An expression relating the rate of a reaction to the concentration of the reactants
Reaction Order and Michaelis-Menten Curve
At low substrate concentrations, the reaction is approximately FIRST-ORDER. At very high substrate concentration, the reaction approximates ZERO-ORDER since the reaction ceases to depend on substrate concentration.
Isotopes
Atoms of the same element that differ in the number of neutrons
One mole of a compound consists of approximately 72g carbon and 6g hydrogen. What is its molecular formula? What is its empirical formula?
Converting to moles gives us six moles of carbon and six moles of hydrogen in one mole of the entire compound. This gives us our molecular formula, C6H6. The empirical formula is the smallest whole-number ratio of the elements making up a molecule. empirical = CH
Fusion
Creation of energy by joining the nuclei of two hydrogen atoms to form helium. Solid --> Liquid
State Functions
Describe the physical properties of an equilibrium state. Are pathway independent. Pressure, density, temp, volume, enthalpy, internal energy, Gibbs free energy, and entropy
Equivalents
Different units of equal measure
Which compound will migrate the fastest during thin layer chromatography using silica plates?
During thin layer chromatography on silica plates, polar molecules are attracted to the silica and migrate slower than non-polar compounds. Of the answer choices, only cyclohexane is non-polar. Choice A is correct. A. Correct. B. Incorrect, ketone group makes this molecule polar. C. Incorrect, the carboxylic acid group is polar. D. Incorrect, the alcohol is polar.
Ionic Bonds
Formed when one or more electrons are transferred from one atom to another - Formed via the transfer of one or more electrons from an element with a relatively low IE to an element with a relatively high electron affinity ΔEN > 1.7.
Compare Hund's rule, the Heisenberg Uncertainty Principle, the Bohr model, and the Rutherford model.
Heisenberg - refers to the inability to know the momentum and position of a single electron simultaneously Bohr Model - an early attempt to describe the behavior of the single electron in a hydrogen atom (Farther orbits =↑ Energy) Rutherford - described a dense, positively charged nucleus, that electrons circulate like planets around the sun Hund's Rule - electrons fill empty robitals first before doubling up electrons in the same orbital
Compound Molecular Formula
Multiple of empirical formula to show exact # of atoms of each element
The formation of α-d-glucopyranose from β-d-glucopyranose is called:
Mutarotation is the interconversion between anomers of a compound.
Sodium hypochlorite (NaClO) is used as a disinfectant and has also been shown to treat chronic skin inflammation. What is the oxidation number of chlorine in NaClO?
+1 In NaClO (sodium hypochlorite), sodium carries its typical +1 charge, and oxygen carries its typical -2 charge. This means that the chlorine atom must carry a +1 charge in order to balance the overall charge of zero.
Definition of Rate
- 2A + B -> C - Negative sign in front of the rate expression for the reactants - Expressed in moles per liter per sec (mol/ L *s) or molarity per sec (M/ s)
Anomer
- Isomers that differ at a new asymmetric carbon atom formed on ring closure - Cyclic monosaccharides or glycosides that are epimers, differing from each other in the configuration of C-1 if they are aldoses or in the configuration at C-2 if they are ketoses. The epimeric carbon in anomers are known as anomeric carbon or anomeric center.
Enantiomerization and Racemization
- are the same thing. - the formation of a mirror-image or optically inverted form of a compound.
Acid Names
-ic: Have one MORE oxygen than -ous. -ous: Has one FEWER oxygen than -ic.
Second Order Reaction
-rate is proportional to either the concentrations of 2 reactants or to the square of the concentrations of a single reactant *Rate = k[A]1[B]1 or rate = k [A]2 or rate = k [B]2 1/([A]) vs time line slope = k
Standard Conditions
298 K, 1 atm, 1 M Note that in gas law calculations, Standard Temperature and Pressure (STP) is 0°C, 1 atm.
hydrolysis reaction
A chemical reaction that breaks apart a larger molecule by adding a molecule of water - Using water to break the bonds in a molecule.
The atomic weight of hydrogen is 1.008 amu. what is the percent composition of hydrogen by isotope assuming that hydrogens only isotopes are 1H and 2D 92% H , 8% D 99.2% H , 0.8% D 99.92% H , 0.08% D 99.992% H ,0.008% D
Set up system of two algebraic equations: where H and D are the percentages of H (mass = 1amu) and D(mass = 2amu) H + D = 1 (percent H + percent D = 100%) 1H + 2D = 1.008 (atomic weight calculation) rearrange 1st equation and substitute into the 2nd yields (1-D) + 2D = 1.008, or D = 0.008. 0.008 is 0.8% so there is 0.8% D
Compound Empirical Formula
Simplest whole-number ratio of atoms.
Consider the following reaction: C6H12O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l) ΔH = - 2808 kJ / mol Under what conditions will this reaction proceed spontaneously?
Spontaneity is determined by a negative ΔG value in Gibbs free energy equation: ΔG = ΔH - TΔS A reaction with a negative ΔH and a positive ΔS will thus be spontaneous under any conditions. The reaction given has a negative ΔH. It also involves converting 1 mole of solid and 6 moles of gas into 6 moles of liquid and 6 moles of gas. That phase change means entropy is increasing (solid to liquid). Thus, with a negative ΔH and a positive ΔS this reaction is spontaneous under any conditions Reactions with a negative ΔH and a negative ΔS are spontaneous at low temperatures (e.g. the freezing of water from liquid to solid). Reactions with a positive ΔH and a positive ΔS are spontaneous at high temperatures (e.g. the boiling of liquid water into steam)
Why is ^6C carbon least likely to be found in nature?
Superscript refers to the mass number of an atom which is equal to the number of protons plus the number of neutrons present in an element. Subscript would be (Z) atomic number According to periodic table carbon contains 6 protons; therefore atomic number is 6. Isotopes all have the SAME number of protons but DIFFER in number of neutronsCarbon is most likely to have a mass number of 12 (6 protons, 6 neutrons) ^6C would mean there are 6 protons and 0 neutrons which would be a highly unstable isotope
Which of the following aqueous solutions will have the highest boiling point? A. 0.10 m Na3PO4 B. 0.15 m NaCl C. 0.20 m HF D. 0.30 m CH3OH
This question is testing your understanding of colligative properties as they relate to boiling-point elevation. The change in temperature for the boiling point of a solution follows the equation ΔTb = Kbmi, where Kb represents the boiling point elevation constant (for water, Kb = +0.52oC/m), m represents the molality of the solution (moles of solute/kg of solvent), and i represents the van't Hoff factor. Since the boiling point elevation is proportional to the molality multiplied by the van't Hoff factor, you must consider each variable in the overall determination. Upon hydration of each sodium phosphate, three Na+ ions and one PO43- ion are produced, giving a van't Hoff factor of 4. Overall, ΔTb = Kb(0.1)(4) = 0.4Kb. For sodium chloride, one Na+ ion and one Cl- ion are produced, yielding a ΔTb = Kb(0.15)(2) = 0.3Kb. Since hydrogen fluoride is a weak electrolyte (weak acid), i=1 and ΔTb = Kb(0.2)(1) = 0.2Kb. Lastly, methanol is a non-electrolyte and does not dissociate in solution, resulting in a van't Hoff factor of one and ΔTb = Kb(0.3)(1) = 0.3Kb. Thus, sodium phosphate will have the highest boiling point making A the correct answer.
decomposition reaction (catabolism)
breaks chemical bonds. Single reactant breaks down 2HgO (s) --> 2Hg (l) + O2 (g)
isobaric process
constant pressure
Isothermal
constant temperature
What is the structure of methyl propanoate?
methyl indicates CH3, propane indicates a 3-carbon chain, "oate" indicates an ester linkage. CH3CH2COOCH3
isotope abundance
more stable isotopes will be found in greater abundance. *more neutrons and longer half-life are evidence of stability
Single-Displacement
one element trades places with another element in a compound: A + BC --> AC + B An atom/ion in a compound is replaced by another atom/ion Cu (s) + AgNO3 (aq) --> Ag (s) + CuNO3 (aq)
pH and pOH
pH + pOH = 14 pH = −log [H+] pOH = −log [OH−]. [H+] = 10 ^-pH ex. a solution with an H+ concentration of 10^−4 M will have a pH of 4, and a solution with an OH− concentration of 10^−9 M will have a pOH of 9.
Electron Affinity (EA)
the energy change associated with the gaining of an electron by an atom in its gaseous state
Gibbs Free Energy
the energy of a system that is available to do work at a constant temperature and pressure ΔG = Ea− Ea rev −ΔG = Exergonic +ΔG = Endergonic
Ionization Energy (IE)
the energy required to remove one electron from a neutral atom of an element
Normality
the number of equivalents of a substance dissolved in a liter of solution Concentration of equivalents in solution. N= # of equivalents/ liters of solution
Molarity
the number of moles of solute per liter of solution
Zeff (effective nuclear charge)
the positive charge/attraction of the nucleus experienced by the valence electrons (increases moving across the periodic table w/ increased # of protons -- makes the atom smaller because the force holds it tight)
Equilibrium Constant
the ratio of product concentrations to reactant concentrations at equilibrium, with each concentration raised to a power equal to the number of moles of that substance in the balanced chemical equation
Double-Displacement (metathesis)
two aqueous molecules exchange cations AB + CD --> AD + CB Elements from two compounds swap places CaCl2 (aq) + 2AgNO3 (aq) --> Ca(NO3)2 (aq) + 2AgCl (s)
Isovolumetric (isochoric)
volume remains constant
Polar Bonds
ΔEN is between 0.5 and 1.7.
EM spectrum
Red Monkeys In Vans Use X-ray Guns radio, micro, infrared, visible, UV, x-ray, gamma
The equillibrium of a rxn can be changed by what factors?
1. adding or subtracting heat - shifts eq based on the enthalpy change of the reaction 2. increasing reactant concentrations - shift the eq in direction of the product 3. reactant concentrations were decreased - shift eq in direction of the reactants 4. changing volume of reactant would affect any rxn with gaseous reactants or products **adding or removing a catalyst would change the reaction rate, it would not change where the equilibrium lies.
Which of the following characterizes butane? A. high solubility in water B. strong dipole moment C. high molecular weight D. low solubility in water
Butane is a four carbon alkane. As such, it is non-polar and low in molecular weight. Solubility in water is primarily governed by polarity and ability to hydrogen-bond, both of which butane lacks. - nonpolar bonds do not dissolve in water well - alkanes lack dipole mmoments - A four carbon alkane has low molecular weight. High molecular weight on the MCAT is often used to describe long-chain polymers and very large molecules, and butane does not qualify for either designation. Choice d is the best choice, low solubility in water.
Aerobic respiration ends at the electron transport chain, where protein complexes are reduced and oxidized in turn as electrons make their way to join O2 to form H2O. Consider the following equation: Which species acts as an oxidizing agent?
C is the correct answer. N in NH3 The oxidizing agent is the species that is reduced in any given equation. In this problem, six hydrogen atoms with +1 oxidation states in NH3 are reduced to three neutral H2 molecules.
Open system
Can exchange BOTH energy and matter with the environment
Which subatomic particle is the most important for determining each of the following properties of an atom? Charge, Atomic number, and isotope.
Charge: Electron # Atomic Number: Proton # Isotope: Neutron #
When is a photon emitted and when is it absorbed?
Emitted when returning to ground state or lower energy level. Electron must lose energy to do so therefore that will require emitting radiation in the form of a photon. Absorbed when going to higher energy level
Adiabatic
Exchange no heat with the environment
Covalent Bond
Formed via the sharing of electrons between two elements of similar EN.
bond order
Refers to whether a covalent bond is a single, double, or triple bond. As bond order increases bond strength increases bond energy increases bond length decreases
Le Chatelier's Principle
If a stress is applied to a system, the system shifts to relieve that applied stress. ex: bicarbonate buffer increase in pH --> increase in respiration to blow off CO2 Increase in pH --> increase in respiration, trapping CO2
Arrhenius equation
K=Ae^(-Ea/RT) where k is the rate constant and A is pre-exponential factor: how often particles collide in correct orientation.
Kinetic (Ea) and Thermodynamic (DG) Control
Kinetic Products: HIGHER in free energy than thermodynamic products and can form at lower temperatures. "Fast" products because they can form more quickly under such conditions. LOWER in free energy than kinetic products, more stable. Slower but more spontaneous (more negative DG)
What is the difference between mass number, atomic number, & atomic weight?
Mass Number(mass of single atom= protons+neutrons) is just slightly less the sum of the masses of protons and neutrons in a given atom of an element. Atoms of the same element with different mass numbers are isotopes of each other. Atomic Number = #of protons ONLY Atomic weight (mass of 1 mole of an element containing isotopes in natural properties) is the weighted average of the naturally occurring isotopes of 1 mole of an element.
Element Properties of Nonmetals
Physical: - Any phase at STP - dull, brittle, poor conductors - opposite of metals Atomic: - high effective nuclear charge - high electronegativity - high ionization energy - small radius
Element Properties of Metalloids
Physical: - Intermediate at STP - shiny, brittle, semiconductor Atomic: intermediate
Element Properties of Metals
Physical: -Solid at STP -shiny, dense, good conductors -malleable Atomic: -Low effective nuclear charge, -Low electronegativity -Low ionization, low radius
Reaction Quotient
Ratio of the concentrations of the products to the concentrations of the reactants at any point during the reaction aside from equilibrium, where each reactant and product in the expression is raised to the power of its stoichiometric coefficient. Commonly denoted by Q. Exclude pure solids and liquids. Q < Keq DG < 0, reaction --> Q = Keq DG = 0, equilibrium Q > Keq DG > 0, reaction <--
Which of the following correctly orders the boiling point of benzaldehyde, benzyl alcohol, and ethyl benzene from highest to lowest?
The greater the molecular weight, the higher the boiling point. Also, the stronger the intermolecular forces, the higher the boiling point. Ethyl benzene forms London dispersion forces and has a molecular weight of 106.2 g/mol. Benzaldehyde has a molecular weight of 106.1 g/mol and forms dipole-dipole forces in addition to London dispersion forces. Lastly, benzyl alcohol has a molecular weight of 108.1 g/mol and forms hydrogen bonds, a special type of dipole-dipole interaction, as well as London dispersion forces. Since all of the molecular weights are approximately the same, the intermolecular forces of each compound will determine the boiling point. Hydrogen bonds (dipole-dipole) in benzyl alcohol are stronger than dipole-dipole forces in benzaldehyde, and all dipole-dipole forces are stronger than London dispersion forces. Therefore, benzyl alcohol (BP: 205.3oC) > benzaldehyde (BP: 178.1oC) > ethyl benzene (BP: 136.0oC), or III > II > I
The behavior of gas will deviate from ideal behaviors LEAST under what conditions?
The ideal gas law, PV=nRT, is based on two assumptions: 1) individual molecular volume is negligible, and 2) intermolecular forces do not exist. A real gas at high temperature and low-pressure conditions, best approximates these two assumptions, and thus the ideal gas law.
Equivalent Mass
The mass of a salt that will supply one mole of positive or negative charge when dissociated completely. Mass of an acid that yields 1 mole of H+ or mass of a base that reacts with 1 mole of H+.
Formal Charge
The number of valence electrons in an isolated atom minus the number of electrons assigned to the atom in the Lewis structure Formal Charge = valence(e-) dots − sticks Dots: Nonbonding e- Sticks: Pair of bonding electrons
Mutarotation
The rapid interconversion between different anomers of a sugar. optical rotation because of the change in the equilibrium between two anomers, when the corresponding stereocenters interconvert. ex. The formation of α-d-glucopyranose from β-d glucopyranose
reaction mechanisms
The series of elementary reactions or steps that take place during the course of a complex reaction
freezing point
The temperature at which a liquid changes into a solid
Amateur chemists make nitrous oxide at home using this (unbalanced) reaction: How many grams of NH4NO3 are required to produce 134.4 L of mixed gas if products are at STP? (Do NOT heat the ammonium nitrate above 240°C or it may detonate)
This solution has 3 steps: 1. balance the equation 2. determine the required number of moles of product and reactant 3. calculate the mass of reactant necessary. The reaction as written is unbalanced. In the balanced equation, 2 moles of H2O and 1 mole of N2O are made for each 1 mole of NH4NO3. 3 moles of product gas result from each mole of reactant. 22.4 L of gas corresponds to 1 mole of gas at STP, and the specified 134.4 L indicates 6 moles of product gases. 6 moles of mixed product gas requires 2 moles of reactant. NH4NO3 weighs 80 g/mole, so 160 g are required. A. 160, correct. 2 moles of NH4NO3 yields 4 moles of H2O and 2 moles of N2O, for 6 moles of mixed product gas occupying 134.4 L at STP.
For the most part, biological pH is slightly basic. However, the stomach is very acidic, and its contents must be swiftly neutralized by basic bicarbonate ions upon entering the small intestine, which has a basic pH. How many liters of 2 M Ba(OH)2 are needed to titrate a 4 L solution of 6 M H3PO4?
Use the equivalence point equation: NaVa = NbVb Ba(OH)2 can dissociate to give two hydroxide ions, so its normality is 2 M × 2 = 4 N. H3PO4 can dissociate to give three hydronium ions, so its normality is 6 M × 3 = 18 N. Plugging into the equation, we get (18 N)(4 L) = (4 N)(Vb). Therefore, Vb is 18 L.
Valence Shell Electron Pair Repulsion Theory (VSEPR)
Valence-shell electron-pair repulsion theory; because electron pairs repel, molecules adjust their shapes so that valence electron pairs are as far apart as possible Electronic Geometry: Bonded and lone pairs treated the same. Molecular Shape: Lone pairs take up less space than a bond to another atom.
What happens when electrons are removed from an element? (for example Zn^2+)
When electrons are removes from an element forming a cation, they will be removed from the sub-shell with the highest n value first. Zn^0 has 30 electrons, so it would have ts regular configuration. The second to last subshell (the one with the highest principal quantum number) is emptied first. then the last subshell.
What is the most common electron configuration for Chromium (Cr)?
[Ne] indicates filled 2s and 2p orbitals, which is incorrect for chromium. [Ar] correctly indicates filled 3s and 3p orbitals. Normally, the 4s would fill with 2 electrons next, followed by 4 electrons in the 3d orbital. However, chromium is an exception which fills 4s1 and 3d5. Copper is a similar exception which fills 4s1 and 3d10 rather than 4s2 and 3d9. These are the two main exceptions you should know for the MCAT. Note that elements in the same periods as Cr and Cu (such as Au, Ag, and Mo) similarly serve as exceptions to the usual rule. [Ar] 4s23d4, incorrect, While this would normally be true, Cr and Cu are exceptions which fill their 3d orbitals to 5 and 10 before placing their last electron in 4s1. [Ar] 4s13d5, correct.
combination reaction (synthesis reaction)
a chemical change in which two or more substances react to form a single new substance
combustion reaction
a chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light - Involves a fuel, usually a hydrocarbon, and O2 (g) Commonly forms CO2 and H2O CH4 (g) + 2O2 (g) --> CO2 (g) + H2O (g)
Nonpolar Bonds
a covalent bond in which electrons are shared equally ΔEN < 0.5.
First Order Reaction
a reaction in which the reaction rate is proportional to the concentration of only one reactant
Arrhenius Equation
an acid as a species that produces H+ in an aqueous solution, and a base as a species that produces OH- in aqueous solution R = 8.314 J/mol K
Sigma and Pi Bonds
describe the patterns of overlap observed when molecular bonds are formed
intermolecular forces
forces of attraction between molecules
Atomic Size
increases from top to bottom within a group and decreases from left to right across a period. - the distance between the outermost electrons and the nucleus
Crystalline Lattices
large organized arrays of ions formed by ionic compounds
What are the 4 quantum numbers?
principal quantum number (n) - max e- is 2n^2 (for any value of n there will be a max of 2n^2 electrons; two per orbital.) Any value 1, 2, 3.. *max e- for subshells is 4l+2) angular momentum quantum number(l) - (values range from 0 to n-1) cannot be higher than n-1. magnetic quantum number (ml) - describes the chemical's magnetic properties can only be an integer value between -l --> l. It cannot be equal to 1 if l = 0; this would imply that an s orbital has 3 subshells (+1, 0, 1) whe we know it can only have 1. spin quantum number (ms) +/- 1/2 (measure of an electron's intrinsic spin) electrons spins are parallel, in that their spins are aligned in the same direction (for both species)
What is the Heisenberg Uncertainty Principle? How is this best explained?
principle: it is impossible to determine simultaneously both the position and velocity of an electron or any other particle Error in one variable is increased by attempts to measure the other.