MCAT general and organic chemistry
in peroxides (such as H₂O₂ or Na₂O₂), oxygen has an oxidation state of
-1
enthalpy
-H -a measure of the heat energy that is released or absorbed when bonds are broken and formed during a reaction that's run at constant pressure
lewis acid
-accepts electrons -electrophile
beta + decay
-also known as positron emission -when an unstable nucleus contains too few neutrons, it converts a proton into a neutron and a positron, which is ejected -the positron is the electron's antiparticle and is identical to an electron expect its charge is positive -increases the number of neutrons -decreases the number of protons -subtracts 1 from the atomic number
gamma decay
-brings an excited nucleus to a lower energy state -doesn't change mass number of atomic number
triple bond stretch
-carbon carbon triple bond -carbon nitrogen triple bond -occurs from 2260-2100
electron capture
-causes the atomic number to be reduced by 1 while the mass number remains the same -the capturing of an electron from the closest electron shell and use it in the conversion of a proton into a neutron -increases the number of neutrons -decreases the number of protons -subtracts 1 from the atomic number
pi bond
-composed of 2 electrons that are localized to the region that lies on opposite sides of the plane formed by the two bonded nuclei and immediately adjacent atoms, not directly between the nuclei as with a sigma bond -formed by the proper, parallel, side to side alignment of two unlocalized p orbitals on adjacent atoms
thin layer chromatography
-compounds are separated based on differing polarities -different compounds travel at different rates -more polar components interact with the polar stationary plate and travel at a slower rate -the less polar components have a greater affinity for the solvent than the stationary plate and travel at a faster rate than the polar components -results are calculated as an Rf value, using a ratio to front value, which is the distance traveled by the individual component divided by the distance traveled by the solvent front
sigma bond
-consists of 2 electrons that are localized between 2 nuclei -formed by the end to end overlap of one hybridized orbital from each of the 2 atoms participating in the bond
lewis base
-donates electrons -nucleophile
hydrogen
-has a +1 oxidation state when bound to something more electronegative to carbon -has a -1 oxidation state when bonded to an atom less electronegative than carbon -has a 0 oxidation state when bonded to carbon
branching
-inhibits van der waals forces by reducing the surface area available for the intermolecular interactions -tends to reduce the attractive forces between molecules and to lower both melting and boiling points
N-H stretch
-moderate -occurs at 3150-2500
kinetic molecular theory
-molecules of a gas are so small compared to the average space between them so that the molecules themselves essentially take up no volume -molecules of a gas are in constant motion -molecules of a gas move at constant speed between collisions and collisions are elastic -molecules of a gas have no intermolecular forces -average kinetic energy of the molecules is directly proportional to the absolute temperature
affinity chromatography
-most commonly used to purify proteins or nucleic acids from complex biochemical mixtures -as a result on specific binding, the target molecule is trapped on the stationary phase, which is then washed to remove the unwanted components of the mixture -target protein is then released off the solid phase in a highly purified state
C-H stretch
-occurs from 3300-2850 -sp3 carbon occurs at 3000-2850 -sp2 carbon occurs at 3150-3000 -sp carbon occurs at 3300
extraction of organic amines
-organic compounds that are basic (amines) can be extracted from mixtures of organic compounds upon treatment with dilute acid (usually 5-10% HCl) -this will protonate the basic functional group forming a positively charged ion -the resulting cationic salts of these basic compounds are usually freely soluble in aqueous solution and can be removed from the organic compounds that remain dissolved in the organic phase
gas chromatography
-partitioning of components to be separated takes place between a mobile gas phase and a stationary liquid phase -partitioning occurs based on different volatilities
carbocation
-positively charged -sp² hybridized -empty p orbital
temperature change
-proportional to the heat absorbed -inversely proportional to the substance's heat capacity
alpha decay
-reduces the parent's atomic number by 2 and the mass number by 4 -decreases the number of neutrons and protons in the nucleus
enolate ion
-resonance stabilized carbanion -negatively charged -nucleophilic
carbonyl stretch (C=O)
-stretch 1 -strong and sharp around 1700
high performance liquid chromatography
-takes advantage of differing affinities of various compounds for either a stationary phase or a mobile phase -the sample to be separated in solubilized and injected by syringe, then the mobile phase carries the sample to the column where is is separated into its components which are detected and analyzed as they exit
standard conditions
-temperature is 298 K (25 C) -pressure is 1 atm -all solids and liquids are assumed pure -solutions are considered to be concentration of 1 M
solubility depends on
-the polarity of the solute -the polarity of the solvent
the amount of heat required to cause a change of phase depends on 2 things
-the type of substance -the amount of substance
radioactive
-unstable nuclei -undergo a transformation to make them more stable
size exclusion chromatography
-used to separate bulk materials based on molecular size -materials are dissolved in solvent and travel to the bottom of a packed column where they are collected
fractional distillation
-used when the difference in boiling points of the components in the liquid mixture is not large -fractional distillation column in packed with material -packing results in the liquid mixture being subjected to different vaporization-condensation cycles
ion exchange chromatography
-used where materials to be separated having varying charge states -utilizes a polymeric resin funtionalized with either positive or negatively charged molecules on the polymer surface -used in separation of mixtures of proteins
O-H stretch
-very strong and broad -occurs at 3600-3200
beta - decay
-when an unstable nucleus contains too many neurons, it may convert a neutron into a proton and an electron (also known as a beta - particle) which is ejected -decreases the number of neutrons and increases the number of protons -adds 1 to the atomic number
extraction of phenols
-when phenols are present in a mixture of organic compounds and need to be removed, a dilute sodium hydroxide solution (usually about 10%) will succeed in converting phenols into their corresponding anionic salts -the anionic salts of the phenols are generally soluble in the aqueous phase and can therefore be removed from the organic phase
the oxidation state of any element in its standard state is
0
the sum of oxidation states of the atoms in a neutral molecule must always be
0
determine the degree of unsaturation of the molecule: C₃H₅Br
1 (since Br is a halogen, count it as a hydrogen)
pressure
1 atm =760 torr = 760 mm Hg = 101.3 kPa
methane
1 carbon
1 milliliter is the same volume as
1 cubic centimeter
one atomic mass unit is equal to exactly
1/12 the mass of an atom of carbon 12
decane
10 carbons
d subshells
10 electrons
Consider the following reaction: 2 Al + 6 HCl → 2 AlCl₃ + 3 H₂ If 108 grams of aluminum metal are consumed, how many grams of hydrogen gas will be produced?
12 grams because the stoichiometric coefficients give the ratios of the number of moles that apply to the combination of reactants and the formation of products - not the ratios by mass - we first need to determine how many moles of aluminum react. since the molecular weight of aluminum is 27, we know that 27 grams of aluminum is equivalent to 1 mole. therefore 108 grams of aluminum is 4 moles. according to the equation, for every 2 moles of aluminum that react, 3 moles of H₂ are produced. so if 4 moles of aluminum react, we'll get 6 moles of H₂. convert the number of moles of H₂ produced to grams. 1 mole of H₂ has a mass of 2 grams. therefore, 6 moles of H₂ will have a mass of 12 grams.
f subshells
14 electrons
determine the degree of unsaturation of the molecule: C₄H₆O
2 (ignore the oxygen)
balance this equation. C₈H₁₈ + O₂ → CO₂ + H₂O
2 C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O
ethane
2 carbons
ethyl group
2 carbons
s subshells
2 electrons
determine the degree of unsaturation of the molecule: C₆H₈
3
isopropyl group
3 carbons
propane
3 carbons
propyl group
3 carbons
balance this equation. NH₃ + O₂ → NO + H₂O
4 NH₃ + 5 O₂ → 4 NO + 6 H₂O
butane
4 carbons
butyl group
4 carbons
sec-butyl group
4 carbons
Consider the following reaction: 2 Al + 6 HCl → 2 AlCl₃ + 3 H₂ How many grams of HCl are required to produce 534 grams of aluminum chloride?
438 grams first, convert the desired mass of AlCl₃ into moles. the molecular weight of AlCl₃ is 133.5. 534 grams of AlCl₃ is equivalent to 4 moles. according to the equation, for every 2 moles of AlCl₃ that are produced, 6 moles of HCl are consumed, so if we want to produce 4 moles of AlCl₃, we will need 12 moles of HCl. the molecular weight of HCl is 36.5 12 moles of HCl will have a mass of 438 grams.
pentane
5 carbons
determine the degree of unsaturation of the molecule: C₂₀H₃₀O
6
hexane
6 carbons
p subshells
6 electrons
avogadro's number
6.02 x 10²³
heptane
7 carbons
octane
8 carbons
nonane
9 carbons
entropy
A measure of disorder or randomness.
charles's law
A principle that describes the relationship between the temperature and volume of a gas at constant pressure
Gamma decay occurs when a nucleus emits: A. a photon. B. a proton. C. a neutron. D. an electron.
A. a photon
In its lowest-energy electron configuration, zinc has a: A. filled 3d energy level and a filled 4s energy level. B. half-filled 3d energy level and a filled 4s energy level. C. filled 3d energy level and a half-filled 4s energy level. D. half-filled 3d energy level and a half-filled 4senergy level.
A. filled 3d energy level and a filled 4s energy level.
Which measurement unit CANNOT be used to express power? A. kg•m2 •s2 B. J•s-1 C. ft•lb •s-1 D. W
A. kg•m2 •s2
Four organic compounds: 2-butanone, n-pentane, propanoic acid, and n-butanol, present as a mixture, are separated by column chromatography using silica gel with benzene as the eluent. What is the expected order of elution of these four organic compounds from first to last? A. n-Pentane → 2-butanone → n-butanol → propanoic acid B. n-Pentane → n-butanol → 2-butanone → propanoic acid C. Propanoic acid → n-butanol → 2-butanone → n-pentane D. Propanoic acid → 2-butanone → n-butanol → n-pentane
A. n-Pentane → 2-butanone → n-butanol → propanoic acid the four compounds have comparable molecular weights, so the order of elution will depends on the polarity of the molecule. increasing the polarity of the eluting molecule will increase its affinity for the stationary phase and increase the elution time.
When a 0.1 M H2SO4 solution is added to pulverized blackboard chalk, the following reaction takes place. CaCO3(s) + H2SO4(aq) CaSO4(s) + CO2(g) + H2O(l) At 25°C, the reaction is spontaneous and has: A. negative ΔG° and positive ΔS°. B. negative ΔG° and negative ΔS°. C. positive ΔG° and negative ΔS°. D. positive ΔG° and positive ΔS°.
A. negative ΔG° and positive ΔS°. because spontaneous reactions always have a -ΔG° and a reaction that creates a gaseous product from solid and liquid reactants must have a positive ΔS°
Knowing that the speed of light in the vitreous humor is 2.1 × 108 m/s, what is the index of refraction of the vitreous humor? (Note: The speed of light in a vacuum is 3.0 × 108 m/s.) A. 0.7 B. 1.4 C. 2.1 D. 3.0
B. 1.4 (3.0 × 108 m/s)/(2.1 × 108 m/s)=1.4
When two amino acids are joined via a peptide bond, what is the mass of the byproduct of this reaction? (Note: Assume that the amino acids were not modified by protecting groups.) A. 17 amu B. 18 amu C. 32 amu D. 44 amu
B. 18 amu the formation of a peptide bond is accompanied by the formation of water as a by-product and the pass of water is 18 amu
Each of the following equations shows the dissociation of an acid in water. Which of the reactions occurs to the LEAST extent? A. HCl + H2O → H3O+ + Cl− B. HPO42− + H2O → H3O+ + PO43− C. H2SO4 + H2O → H3O+ + HSO4− D. H3PO4 + H2O → H3O+ + H2PO4−
B. HPO42− + H2O → H3O+ + PO43−
The equilibrium BaCrO4(s) Ba2+(aq) + CrO42-(aq) exists in a saturated aqueous solution of BaCrO4. Dissolution of Na2CrO4 in a saturated aqueous BaCrO4 solution would: A. have no effect on the position of this equilibrium. B. shift this equilibrium left. C. shift this equilibrium right. D. shift this equilibrium first right and then left.
B. shift this equilibrium left.
A 60-Ω resistor is connected in parallel with a 20-Ω resistor. What is the equivalent resistance of the combination? A. 80 Ω B. 40 Ω C. 15 Ω D. 3 Ω
C. 15 Ω The answer to this question is C because the equivalent resistance is given by the expression (1/(60) + 1/(20))-1 = 15 .
Which of the following will decrease the percentage ionization of 1.0 M acetic acid, CH3CO2H(aq)? A. Chlorinating the CH3 group B. Diluting the solution C. Adding concentrated HCl(aq) D. Adding a drop of basic indicator
C. Adding concentrated HCl(aq)
The term "ideal gas" refers to a gas for which certain assumptions have been made. Which of the following is such an assumption? A. The law PV = nRT2 is strictly obeyed. B. Intermolecular molecular forces are infinitely large. C. Individual molecular volume and intermolecular forces are negligible. D. One gram-mole occupies a volume of 22.4 L at 25°C and one atmosphere pressure
C. Individual molecular volume and intermolecular forces are negligible.
Why is the velocity of blood flow slower in capillaries than in arteries? A. Capillary walls are more elastic than arterial walls. B. Capillaries have less resistance to blood flow than arteries. C. The total cross-sectional area of capillaries exceeds that of arteries. D. Blood pressure is higher in the capillaries than in arteries.
C. The total cross-sectional area of capillaries exceeds that of arteries
What must be true about a spontaneous, endothermic reaction? a. ∆H is negative b. ∆G is positive c. ∆S is positive d. ∆S is negative
C. ∆S is positive
acetate (AcO⁻)
CH₃CO₂⁻
cyanide
CN⁻
carbonate
CO₃ ⁻²
perchlorate
ClO₄⁻
balance this equation. CuCl₂ + NH₃ + H₂O → Cu(OH)₂ + NH₄Cl
CuCl₂ + 2 NH₃ + 2 H₂O → Cu(OH)₂ + 2 NH₄Cl
balance this equation. C₃H₈ + O₂ → CO₂ + H₂O
C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O
What volume of a 0.120 M CaI2 solution would contain 0.078 mol of the solute? A. 35.0 mL B. 65.0 mL C. 350 mL D. 650 mL
D. 650 mL 0.078 mol x (L/0.120 mol) = 0.650 L x (1000 mL/1 L)
The relative thermodynamic stability of isomeric organic compounds can be inferred from which of the following types of experimental data? A. Boiling points B. UV-visible absorption spectra C. Mass spectroscopic fragmentation patterns D. Heats of combustion
D. Heats of combustion
Which experimental condition is NOT necessary to achieve reliable data for Michaelis-Menten enzyme kinetics? A. Initial velocity is measured under steady state conditions. B. Solution pH remains constant at all substrate concentrations. C. The concentration of enzyme is lower than that of substrate. D. The reaction is allowed to reach equilibrium before measurements are taken.
D. The reaction is allowed to reach equilibrium before measurements are taken.
That the electric field is uniform between the electrodes means that the electric field lines: A. are more closely spaced at the positive electrode than at the negative one. B. intersect halfway between the electrodes. C. are more closely spaced at the negative electrode than at the positive one. D. are equally spaced at both electrodes and between them.
D. are equally spaced at both electrodes and between them.
Which of the following types of orbitals of the central atom are involved in bonding in octahedral compounds? A. sp B. sp3 C. p D. d2 sp3
D. d2 sp3
Which statement correctly describes how enzymes affect chemical reactions? Stabilization of: A. the substrate changes the free energy of the reaction. B. the transition state changes the free energy of the reaction. C. the substrate changes the activation energy of the reaction. D. the transition state changes the activation energy of the reaction.
D. the transition state changes the activation energy of the reaction.
Determine the oxidation state of SF₄
F has an oxidation state of -1, so S has an oxidation state of +4
bicarbonate
HCO₃⁻
hydronium
H₃O⁺
ammonium
NH₄⁺
nitrite
NO₂⁻
nitrate
NO₃⁻
hydroxide
OH⁻
boyle's law
P1V1=P2V2
phosphate
PO₄ ⁻³
ideal gas law
PV=nRT P=pressure of gat in atm V=volume of container in liters n=number of moles of gas R=universal gas constant (0.0821) T=absolute temperature of gas in Kelvins
sulfite
SO₃ ⁻²
sulfate
SO₄ ⁻²
enthalpy
The heat content of a system at constant pressure
degree of saturation formula
[(2n+2)-x]/2 n=number of carbons x=number of hydrogens
What is the electron configuration of Argon (atomic number 18)?
[Ar]=1s²2s²2p⁶3s²3p⁶
sigma bond
a bond formed when two atomic orbitals combine to form a molecular orbital that is symmetrical around the axis connecting the two atomic nuclei
aldol condensation
a classic reaction in which the enolate ion of one carbonyl compound reacts with the carbonyl group of another carbonyl compound
strong nuclear force
a force that holds the protons and neutrons together in a nucleus
electronegativity
a measure of an atom's ability to pull electrons to itself when it forms a covalent bond
excited state
a molecule that has absorbed a photon and given more energy
epimers
a subclass of diastereomers that differ in their absolute configuration at a single chiral center
catalyst
a substance that increases the rate of a reaction without being consumed
angstrom
a unit of length equal to 10⁻¹⁰ m
The H NMR spectrum for Compound X shows one peak at 7.4 ppm. If elemental analysis shows that the compound has an empirical formula of CH, how many possible stereoisomers could Compound X have? a. 0 b. 2 c. 2 d. 4
a. 0 one signal on the H NMR spectrum tells us that the molecule has only one type of hydrogen. since the empirical formula of compound X is CH and the molecule contains no electronegative elements to shift the signal downfield, the single peak, located in the region common for aromatic hydrogens, must represent an aromatic H. any compound with only aromatic Hs must have carbons that are all sp² hybridized, and as such will have no stereoisomers. in this case, the compound is benzene (C₆H₆)
If the pH of carbonated water (water with dissolved carbon dioxide) is 5, what is the hydrogen ion concentration? a. 1 x 10⁻⁵ M b. 5 M c. 5 x 10⁻⁵ M d. 1 x 10⁵ M
a. 1 x 10⁻⁵ M
Ionated oleic acid, containing radioactive iodine-131, is administered orally to study a patient's pancreatic function. If ¹³¹I has a half life of 8 days, how long after the procedure will the amount of ¹³¹I remaining in the patient's body be reduced to 1/5 its initial value? a. 19 days b. 32 days c. 40 days d. 256 days
a. 19 days although the fraction 1/5 is not a whole number power of 1/2, we do know that it's between 1/4 and 1/8. if 1/4 of the sample were left, we'd know that 2 half lives had elapsed, and is 1/8 of the sample were left, we'd know that 3 half lives had elapsed. therefore, because 1/5 is between 1/4 and 1/8, we know that the amount of time will be between 2 and 3 half lives. since each half life is 8 days, this amount of time will be between 12 and 24 days.
Radiolabeled vitamin B₁₂ containing radioactive cobalt-58 is administered to diagnose a defect in a patient's vitamin-B₁₂ absorption. If ⁵⁸Co has a half life of 72 days, approximately what percentage of the radioisotope will still remain in the patient a year later? a. 3% b. 5% c. 8% d. 10%
a. 3% one year is equal to approximately 5 half lives of this radioisotope, since 5x72=360 days=1 year. after 5 half lives, the amount of the radioisotope will drop to (1/2)⁵=1/32 of the original amount administered. because 1/32=3/100=3%, the best choice is A
What is the formula weight of calcium phosphate, Ca₃(PO₄)₂? a. 310 amu b. 350 amu c. 405 amu d. 450 amu
a. 310 amu
Consider the following reaction: CS₂ + 3 O₂ → CO₂ + 2 SO₂ How much carbon disulfide must be used to produce 64 grams of SO₂? a. 38 g b. 57 g c. 76 g d. 114 g
a. 38 g the molecular weight of SO₂ is 64. according to the equation, for every 1 mole of CS₂ that reacts, 2 moles of SO₂ are produced. to just produce 1 mole of SO₂, we need 1/2 mole of CS₂. the molecular weight of CS₂ is 76. 1/2 mole of CS₂ has a mass of 38 grams.
What is the percent composition by mass of carbon in glucose, C₆H₁₂O₆? a. 40% b. 50% c. 67% d. 75%
a. 40% the empirical formula of the compound is CH₂O. the empirical molecular weight is 30. carbon's contribution to the total mass is 12/30=40%
Which single bond present in nitroglycerin is most likely the shortest? A. C-H B. C-O C. C-C D. O-N
a. C-H All of the bonds listed are single bonds. Since hydrogen has a much smaller atomic radius than second period elements, the covalent bond between C and H is shorter than any of the other bonds listed.
Which saturated fatty acid is the most soluble in water? a. CH3(CH2)10COOH b. CH3(CH2)12COOH c. CH3(CH2)14COOH d. CH3(CH2)16COOh
a. CH3(CH2)10COOH the fatty acid that is the most soluble in water will have the shortest alkyl chain
What is the empirical formula for ethylene glycol, C₂H₆O₂? a. CH₃O b. CH₄O c. CH₆O d. C₂H₆O₁
a. CH₃O divide each subscript by the common factor of 2
Carbon atoms with nonbonding electrons are excellent lewis bases/ligands. therefore, which of the following molecules is not a potential lewis base/ligand? a. CO₂ b. CO c. CN- d. CH₃-
a. CO₂ choice A is not a good ligand since all carbon electrons are bonded.
Rank the following from highest to lowest boiling point: I. H₂SO₄ II. NH₃ III. CO₂ IV. H₂O a. I > IV > II > III b. II > I > IV > III c. I > III > IV > II d. IV > III > I > II
a. I > IV > II > III
A pure sample of which of the following ions/molecules will participate in intermolecular hydrogen bonding? I. CH₃CO₂H II. CO₂ III. H₂S a. I only b. III only c. I and II d. I and III
a. I only in order to participate in intermolecular hydrogen bonding, a molecule must be able to act as both a hydrogen bond donor and acceptor. in order to act as a hydrogen bond donor, a molecule must possess a hydrogen atom covalently bound to a nitrogen, oxygen, or fluorine atom. in order to act as a hydrogen bond acceptor, a molecule must have an oxygen, nitrogen, or fluorine atom with an unshared pair of electron. CH₃CO₂H meets both of these requirements, and is therefore a valid choice. CO₂ does not possess any hydrogen atoms and is therefore an invalid option. while H₂S may seem like an enticing choice, sulfur is not sufficiently electronegative to produce hydrogen bonding when covalently bound to hydrogen atoms
Which of these molecules has the strongest dipole moment? a. PBr₃O b. PF₅ c. CCl₄ d. SF₆
a. PBr₃O a bond has a dipole moment when the two atoms in the bond differ in the electronegativity. however, an entire molecule can only have a dipole if it contains bond dipoles and is asymmetrical. choice A is tetrahedral and not all four substituents are the same. therefore, it is asymmetrical and has a small negative dipole in the direction of the most electronegative substituent, oxygen. the remaining choices are trigonal bipyramidal, tetrahedral, and octahedral respectively. all have identical substituents, are symmetrical, and have no net dipole moment.
Which of these modes of radioactive decay causes a change in the mass number of the parent nucleus? a. alpha b. beta - c. beta + d. gamma
a. alpha
An atom with 7 neutrons and a mass number of 12 is an isotope of what element? a. boron b. nitrogen c. magnesium d. potassium
a. boron
If an element had a lewis dot structure of a 4 dots, one on each side, among the follow, this element could represent: a. carbon b. nitrogen c. sulfur d. argon
a. carbon since there are four dots in the lewis symbol, the element will be an element in Group 4 of the periodic table. of the choices given, only carbon is in Group 4.
An understanding of intermolecular forces is of critical importance because they govern so many physical properties of a substance. The property least likely to be influenced by intermolecular force strength is: a. color b. melting point c. solubility d. vapor pressure
a. color
Certain species of fish use electroperception (wherein electrons are discharged from cells in the tail, and flow along lines of force to cells in the head that can detect electron flow patterns) to detect objects around them. Which of the following statements is LEAST likely to be true? a. electroperception is limited to aquatic environments because the resistivity of air is so low b. saltwater fish are more likely to be capable of electroperception than are freshwater fish c. electroperceptive fish can detect objects 1m or 10m away with unequal sensitivity d. electroperception is more likely to be used by fish in turbid or deep-sea environments
a. electroperception is limited to aquatic environments because the resistivity of air is so low since electric fields rely on the generation of electric currents, electric fields from biological sources will not be able to form where the resistivity of the medium is high (like in the air). since the resistivity of the air is too HIGH.
Denver is at a higher altitude than Los Angeles and therefore the atmosphere pressure is lower in Denver than in Los Angeles. Compared to Los Angeles, the melting point of water in Denver will be: a. higher b. lower c. the same d. undetermined from the information given
a. higher
Determine the hybridization of the central atom in each of the following molecules or ions a. H₂O b. SO₂ c. NH₄⁺ d. PCl₃ e. CO₃²⁻
a. hybridization of O is sp3 b. hybridization of S is sp2 c. hybridization of N is sp3 d. hybridization of P is sp3 e. hybridization of C is sp2
The polarity of a solvent, which is commonly defined by the solvent's dielectric constant, E, is one factor that determines the spontaneity of dissolution of a solute in that solvent. NaCl will more readily dissolve in a solvent with a high E than one with a low E because: a. molecules of solvents with high E can orient themselves between ions, thereby attenuating the electrostatic force one ion exerts on another b. molecules of solvents with low E are always aprotic, which means they cannot participate in hydrogen bonding and are more reactive c. in solvents with high E, it takes more energy to remove the ions from the surface of the NaCl crystal than what is gained from the solvation of the Na+ and Cl- ions d. in solvents with low E, it takes energy equal to the lattice free energy of NaCl to break the attractions between Na+ and Cl- ions and create a salvation shell
a. molecules of solvents with high E can orient themselves between ions, thereby attenuating the electrostatic force one ion exerts on another
The flow of sodium into neurons of the optic nerve during an action potential is associated with a: a. negative change in Gibb's free energy and a positive change in entropy b. negative change in Gibb's free energy and a negative change in entropy c. positive change in Gibb's free energy and a negative change in entropy d. positive change in Gibb's free energy and a positive change in entropy
a. negative change in Gibb's free energy and a positive change in entropy Gibb's free energy is negative for spontaneous processes. As well, the movement of particles (like sodium ions) from a region of high concentration to a region of low concentration is associated with an increase in entropy.
Proinsulin must undergo cleavage by protease, resulting in the two smaller units that become functional insulin. Protease's action represents modification of proinsulin's: a. primary structure b. secondary structure c. tertiary structure d. quaternary structure
a. primary structure
Which of the following hybridizations is NOT possible for 2 different carbon atoms in a molecule with molecular formula C4H8? a. sp and sp3 b. sp2 and sp2 c. sp2 and sp3 d. sp3 and sp3
a. sp and sp3 a carbon atom that is involved in a triple bond has sp hybridization. since there is no possibility for C4H8 to have a triple bond, a carbon atom with sp hybridization is not possible for this molecular formula
Determine the orbital geometry and predict the shape of each of the following molecules: a. H₂O b. SO₂ c. NH₄⁺ d. PCl₃ e. CO₃²⁻
a. tetrahedral, bent shape b. trigonal planar, bent c. tetrahedral, tetrahedral d. tetrahedral, trigonal pyramid c. trigonal planar, trigonal planar
If a reaction involving two reactants is first-order with respect to each of those reactants, which of the following is true? a. the net reaction equation is considered second-order b. the reaction rate will not change with addition of either reactant c. both reactants are consumed at the same rate in the reaction d. the reaction rate will only change when the concentrations of reactants changes
a. the net reaction equation is considered second-order
Which of the following about human fertilization is correct? a. the oocyte does not complete meiosis until after fertilization b. all of the lysosomes in a zygote are derived from the sperm c. polyspermy is blocked by the release of large amounts of potassium ions d. the zygote begins growing immediately and doubles in size before it starts dividing
a. the oocyte does not complete meiosis until after fertilization
At 1 atm, deionized water can remain a liquid at temperatures down to -42°C. If a foreign body is added to the supercooled liquid, it will immediately turn into ice. Which of the following is true about this process? a. the reaction is exothermic b. tap water could also be supercooled to -42°C c. the transformation of a supercooled fluid to a solid is nonspontaneous d. water's unique phase diagram allows it to be supercooled
a. the reaction is exothermic
Which of the following proteins binds calcium to initiate cardiac muscle contraction? a. troponin b. myosin c. actin d. tropomyosin
a. troponin
Of the events listed, which occurs first during action potential generation? a. voltage gated sodium channels open at the axon hillock b. hyper polarization stimulated the opening of ligand gated potassium channels d. calcium influx stimulated vesicle fusion and release of neurotransmitter
a. voltage gated sodium channels open at the axon hillock graded potentials occur in the cell body and dendrites, not the axon
Americium-241 is used to provide intracavitary radiation for the treatment of malignancies. This radioisotope is known to undergo alpha decay. What is the daughter nucleus? a. ²³⁷Np b. ²⁴¹Pu c. ²³⁷Bk d. ²⁴³Bk
a. ²³⁷Np alpha decay will reduce the mass by 4 to 237. it will reduce the nuclear charge by 2 from 95 to 93
catalyst
accelerates a reaction by lowering the activation energy of the rate determine step and therefore the energy of the highest energy transition state
Ka > Kb
acid
energy of activation for reaction
activated complex minus the energy of the reactants
alkane
all carbon-carbon bonds are single
dispersion forces are experienced by
all molecules, but experienced more strongly in larger and heavier atoms
extraction
allows the separation of one substance from a mixture of substances by adding a solvent in which the compound of interest is highly soluble
sucrose
alpha 1,2
maltose
alpha 1,4
starch
alpha 1,4
glycogen
alpha 1,4 with alpha 1,6 branch
alkyl substituents
always electron-donating groups
what is the functional group that forms during peptide bond formation
an amide group
diamagnetic
an atom that has all of its electrons spin paired
oxidation occurs at the
anode
beta decay
atomic number increases by 1
network solid
atoms connected in a lattice of covalent bonds meaning that all interactions between atoms are covalent bonds
Which one of the following fatty acids has the highest melting point? a. (3E, 5E)-octa-3,5-dienoic acid b. (3E, 5E)-deca-3,5-dienoic acid c. (3Z, 5Z)-octa-3,5-dienoic acid d. (3Z, 5Z)-deca-3,5-dienoic acid
b. (3E, 5E)-deca-3,5-dienoic acid
What is the electron holding capacity of a pi bond? a. 1 b. 2 c. 4 d. 6
b. 2
Increasing the pressure on the eardrum by 35 kPa can cause it to burst. How deep would a diver have to dive in fresh water to burst his eardrum? a. 1.25 meters b. 3.57 meters c. 6.99 meters d. 10.21 meters
b. 3.57 meters hydrostatic pressure is expressed by Phydro=pgh. for the diver's eardrum to burst, Phydro must equal 35 pKa or 35 x 10³ kg/ms². the question asks for depth, so rearrange and solve for h: h=Phydro/pg h=35 pKa/(1000 x 9.8)=3.5 m
What happens when a container of liquid water (holding 100 moles of H₂O) at 0°C completely freezes? (notes ∆Hfusion=6 kJ/mol, and ∆Hvap=41 kJ/mol) a. 600 kJ of heat is absorbed. b. 600 kJ of heat is released c. 4100 kJ of heat is absorbed d. 4100 kJ of heat is released
b. 600 kJ of heat is released in order for ice to melt, it must absorb heat, therefore the reverse process, water freezing into ice, must release heat. this eliminates A and C. the heat of transition from liquid to solid is -∆Hfusion, so in this case the heat of transition is q=(100 mol)(-6 kJ/mol)=-600 kJ, so choice B is correct
If a student began with 83.2 g of copper (II) sulfate pentahydrate (CuSO₄ x 5H₂O) how much Cu₂I₂ could be made? (Note: the molecular weights of CuSO₄ x 5H₂O and Cu₂I₂ are 249.5 g and 380.8 g, respectively) a. 31.8 b. 63.5 c. 127 g d. 190 g
b. 63.5 since the molecular weight of copper (II) sulfate pentahydrate is given as 249.5 g, 83.2 g of it would be about 1/3 mol. 1/3 of a mol of copper (II) pentahydrate would provide 1/3 of a mole of copper (II). this amount would make 1/6 mol of Cu₂I₂ since each mol requires 2 moles of copper reactant. the molecular weight of Cu₂I₂ is 380.8 g. Dividing this by 6 gives 63.5 g.
Which of the following is a characteristic of mRNA? a. anticodon b. 7-methylguanosine cap c. 60S and 40S subunits d. cloverleaf secondary structure
b. 7-methylguanosine cap
Cesium-137 has a half life of 30 years. How long will it take for only 0.3 grams to remain from a sample that had an original mass of 2.4 g? a. 60 years b. 90 years c. 120 years d. 240 years
b. 90 years since 0.3 grams is 1/8 of 2.4 grams, the question is asking how long will it take for the radioisotope to decrease to 1/8 of its original amount. we know that this requires 3 half lives, since 1/2 cubed is 1/8. so if each half life is 30 years, the 3 half lives will be 3x30=90.
Metabolic flux through the citric acid cycle would likely experience the greatest decrease if the concentration of which of the following were increased? a. ADP b. ATP c. NAD⁺ d. FAD⁺
b. ATP
Infrared spectroscopy could be used to discern which two molecules from each other? I. an anime and an imine II. an alcohol and a carboxylic acid III. glucose and fructose a. II only b. I and II only c. I and III only d. I, II, and III
b. I and II only
Consider the following reaction: 2 ZnS + 3 O₂ → 2 ZnO + 2 SO₂ If 97.5 grams of zinc sulfide undergoes this reaction with 32 grams of oxygen gas, what will be the limiting reagent? a. ZnS b. O₂ c. ZnO d. SO₂
b. O₂ since the molecular weight of ZnS is 97.5 and the molecular weight of O₂ is 32, this reaction begins with 1 mole of both ZnS and O₂. according to the equation, 1 mole of ZnS would react completely with 1.5 moles of O₂. because we only have 1 mole of O₂, the O₂ will be consumed first and will be the limiting reagent. both C and D can be eliminated immediately since a limiting reagent is always a reactant.
What's the electron configuration of a zirconium atom (Z=40)? a. [Kr]4d⁴ b. [Kr]5s²4d² c. [Kr]5s²5p² d. [Kr]5s²5d²
b. [Kr]5s²4d²
Which of the following oxidative transformations is unlikely to occur? a. a primary alcohol to an aldehyde b. a tertiary alcohol to a ketone c. an aldehyde to a carboxylic acid d. a secondary alcohol to a ketone
b. a tertiary alcohol to a ketone oxidation of tertiary alcohols is difficult because it involves C-C bond breaking
An oncogene is a gene whose activation causes a cell to become cancerous. An oncogene is most likely to inhibit: a. mitosis b. apoptosis c. oxidative phosphorylation d. transcription
b. apoptosis
Which of the following best describes the intramolecular bonding present within a cyanide ion (CN-)? a. ionic bonding b. covalent bonding c. van der waals forces d. induced dipole
b. covalent bonding
What could make the following nonspontaneous endothermic reaction spontaneous? 2H₂O (l) → 2H₂ (g) + O₂ (g) a. decreasing volume b. increasing temperature c. decreasing temperature c. the reaction will always be nonspontaneous
b. increasing temperature
A carbonyl group contains what type of bonding interaction (s) between the C and O atoms? a. one sigma bond only b. one sigma and one pi bond only c. one pi bond only d. one sigma and two pi bonds only
b. one sigma and one pi bond only
Of the following, which has the smallest atomic radius? a. sodium b. oxygen c. calcium d. silicon
b. oxygen the atoms with the smallest atomic radius are in the upper right portion of the periodic table.
During the electrolysis of liquid water into hydrogen and oxygen gas at standard temperature and pressure, energy is: a. absorbed during the breaking of H-H bonds and the reaction is spontaneous b. released during the formation of H-H bonds and the reaction is nonspontaneous c. absorbed during the formation of O=O bonds and the reaction is spontaneous d. released during the breaking of O-H bonds and the reaction is nonspontaneous
b. released during the formation of H-H bonds and the reaction is nonspontaneous
What is the percent composition by mass of each element in sodium azide, NaN₃? a. sodium 25%, nitrogen 75% b. sodium 35%, nitrogen 65% c. sodium 55%, nitrogen 45% d. sodium 65%, nitrogen 35%
b. sodium 35%, nitrogen 65% the molecular weight of the compound is 65. sodium's contribution of the total mass can be calculated by 23/65 = ~1/3 = ~33%
The citric acid cycle consists of reactions that break down acetate into carbon dioxide. Given that some steps are thermodynamically unfavorable, why does the cycle proceed in the forward direction overall? a. the rate constant for the unfavorable reactions is very large b. the cycle contains exergonic reactions that drive the endergonic reactions forward c. the endothermically unfavorable reactions also have a negative entropy change d. the activation energies of the unfavorable reactions are lowered by catalysts
b. the cycle contains exergonic reactions that drive the endergonic reactions forward
Which of the following processes would have a negative ∆S? a. the evaporation of a liquid b. the freezing of a liquid c. the melting of a solid d. the sublimation of a solid
b. the freezing of a liquid
In purifying hemoglobin from human red blood cells, a biochemist suspects that some of the molecules have lost their quaternary structure. If she used a gel filtration column to separate the denatured and non-denatured proteins: a. the denatured protein would elute first b. the non-denatured protein would elute first c. the denatured and non-denatured proteins would elute together d. the denatured protein would bind to the adsorbent and not elute
b. the non-denatured protein would elute first
What are the structural features possessed by storage lipids? a. two fatty acids ester-linked to a single glycerol plus a charged head group b. three fatty acids ester-linked to a single glycerol c. two fatty acids ester-linked to a single sphingosine plus a charged head group d. three fatty acids ester-linked to a single sphingosine
b. three fatty acids ester-linked to a single glycerol
Which of the following colors would appear as a bright band in an emission spectrum of a yellow sodium vapor lamp? a. yellow, indicating a lesser wavelength than ultraviolet light b. yellow, indicating a greater wavelength than ultraviolet light c. blue, indicating a lesser wavelength than ultraviolet light d. blue, indicating a greater wavelength than ultraviolet light
b. yellow, indicating a greater wavelength than ultraviolet light
A certain radioactive isotope is administered orally as a diagnostic tool to study pancreatic function and intestinal fat absorption. This radioisotope is known to undergo beta - decay, and the daughter nucleus is xenon-131. What is the parent radioisotope? a. ¹³¹Cs b. ¹³¹I c. ¹³²I d. ¹³²Xe
b. ¹³¹I eliminate choices C and D since the mass number should remain the same for all forms of beta - decay.
Vitamin B₁₂ can be prepared with radioactive cobalt (⁵⁸Co), a known beta + emitter, and administered orally as a diagnostic tool to test for defects in intestinal vitamin B₁₂ absorption. What is the daughter nucleus of ⁵⁸Co? a. ⁵⁷Fe b. ⁵⁸Fe c. ⁵⁹Co d. ⁵⁹Ni
b. ⁵⁸Fe all types of beta + decay leaves the mass of the daughter and parent elements the same, thus the mass must be 58, making B the only option
If it's discovered that a certain non spontaneous reaction becomes spontaneous if the temperature is lowered, then which of the following must be true? a. ∆S is negative and ∆H is positive b. ∆S is negative and ∆H is negative c. ∆S is positive and ∆H is positive d. ∆S is positive and ∆H is negative
b. ∆S is negative and ∆H is negative
Kb > Ka
base
non polar molecules interact
because of an attractive force known as the london dispersion force, one of the van der waals forces
cellulose
beta 1,4
lactose
beta 1,4
energy is needed to
break a bond
phase changes are the result of
breaking or forming intermolecular interactions
Which of the following gives the electron configuration of an aluminum atom? a. 1s²2s²2p¹ b. 1s²2s²2p² c. 1s²2s²2p⁶3s²3p¹ d. 1s²2s²2p⁶3s²3p²
c. 1s²2s²2p⁶3s²3p¹
What is the percent by mass of water in the hydrate MgCl₂ x 5H₂O? a. 27% b. 36% c. 49% d. 52%
c. 49% the formula weight for the hydrate is 185.3. since water's total molecular weight in this compound is 90, water's contribution to the total mass is 90/185.3, which is slightly less than 50%.
A test cross is performed for a particular gene. What percentage of offspring should express the dominant phenotype is the test subject is a heterozygote for that gene? a. 100% b. 75% c. 50% d. 0%
c. 50%
36 Cl primarily decays by beta minus decay. Which of the following is the primary product of 36 Cl decay? a. S b. P c. Ar d. Cl
c. Ar beta minus decay is essentially the conversion of a neutron into a proton and a beta-minus particle. here, the atomic number of the daughter nucleus will be one higher than that of the parent and the correct answer will be C.
Which of the following substances does NOT have a heat of formation equal to zero at standard conditions? a. F₂ (g) b. Cl₂ (g) c. Br₂ (g) d. I₂ (s)
c. Br₂ (g) heat of formation is zero for a pure element in its natural phase at standard conditions. all of the choices are in their standard state, except for bromine, which is a liquid, not a gas, at standard conditions
Which of the following strands of DNA has the highest pyrimidine content? a. ATATGATGAT b. ATCGATCGAT c. CGATCGATCC d. CGCGATCGCG
c. CGATCGATCC
Of the following, which one will have the lowest melting point? a. MgO b. CH₄ c. Cr d. HF
c. CH₄ almost all ionic compounds are solids at room temperature. therefore, choice A is eliminated. similarly, all metals except for mercury (Hg) are solids at room temperature, so eliminate choice C. both answers B and D will be molecular solids. hydrogen fluoride is able to hydrogen bond and will therefore have stronger intermolecular interactions that the non polar membrane. since choice B has the weakest intermolecular, it will be easiest to melt.
All of the following would be categorized as having tetrahedral orbital geometry EXCEPT: a. NH₃ b. NH₄⁺ c. CO₂ d. CH₄
c. CO₂
Which of the following elements would be most strongly attracted to a magnetic field? a. Mg b. Ca c. Cr d. Zn
c. Cr paramagnetic atoms are attracted to magnetic fields.
What is the empirical formula of a compound that is, by mass, 90% carbon and 10% hydrogen? a. CH₂ b. C₂H₃ c. C₃H₄ d. C₄H₅
c. C₃H₄ a 100 gram sample of this compound would contain 90 g of C and 10 g of H. since the atomic weight of C is 12 and that of H is 1, we can find the number of moles of carbon by calculating (90 g C)/(12 g/mol) = 15/2 and number of moles of hydrogen by calculating (10 g H)/(1 g/mol) = 10. the ratio of the amount of carbon to the amount of hydrogen is (15/2)/10=3/4
Which of the following correctly describes the physical properties of water? I. the hydrogen bonds in water result in a lower boiling point than H₂S II. water has a high specific heat due to the hydrogen bonding between molecules III. as pressure increases liquid water is favored over solid water a. II only b. III only c. II and III only d. I, II, and III
c. II and III only
Which of the following represents the correct ground state electronic configuration for ferrous ion, Fe²⁺? a. [Ar]4s²3d⁶ b. [Ar]4s²3d⁴ c. [Ar]3d⁶ d. [Ar]4s²3d²
c. [Ar]3d⁶
Which of the following statements is true? a. catalysts decrease the activation energy of the forward reaction only b. catalysts decrease the activation energy of the reverse reaction only c. catalysts decrease the activation of both the forward and reverse reactions d. catalysts decrease the activation energy of the forward reaction and increase the activation energy of the reverse reaction
c. catalysts decrease the activation of both the forward and reverse reactions
Which of the following energy conversions best describes what takes place in a battery-powered resistive circuit when the current is flowing? A. Electric to thermal to chemical B. Chemical to thermal to electric C. Electric to chemical to thermal D. Chemical to electric to thermal
c. chemical to electric to thermal
Which of these phase changes releases heat energy? a. melting b. fusion c. condensation d. sublimation
c. condensation
When an atom of plutonium-239 is bombarded with an alpha particle, this element along with one free neutron is created: a. californium-240 b. californium-241 c. curium-242 d. curium-243
c. curium-242
A researcher attempts to determine the specific heat of a substance by gradually heating a sample of it over time and measuring the temperature change. His first trial fails because it produces no significant change in temperature. Which changes to his experimental procedure would be most effective in producing a larger temperature change in his second trial? a. increasing the mass of the sample and increasing the heat input b. increasing the mass of the sample and decreasing the heat input c. decreasing the mass of the sample and increasing the heat input d. deceasing the mass of the sample and decreasing the heat input
c. decreasing the mass of the sample and increasing the heat input since ∆T=g/mc, to increase ∆T, the researcher should increase q and decrease m.
During mitosis, the nuclear membrane disintegrates: a. during prophase, and reforms during anaphase b. during metaphase, and reforms during telophase c. during prophase, and reforms during telophase d. during metaphase, and reforms during anaphase
c. during prophase, and reforms during telophase
Metallic chapter results from an element's ability to lose electrons. On the periodic table it is expected that metallic character increases: a. from left to right, because the decrease in electronegativity would make it easier to lose electrons b. from left to right, because the decrease in atomic radius would result in more stable positive ions c. from right to left, because the decrease in ionization energy would make it easier to lose electrons d. from right to left, because the decrease in electron affinity would result in more stable positive ions
c. from right to left, because the decrease in ionization energy would make it easier to lose electrons
Cytosolic proteins intended for the lysosome have a mannose-6-phosphate group attached to them. Those tags are attached in the: a. nucleus b. endoplasmic reticulum c. golgi apparatus d. lysosome
c. golgi apparatus
Which of the following most specifically accounts for neon's ability to form a solid at 1 am and 25 K? a. gravitational forces b. electrostatic forces c. london dispersion forces d. strong nuclear forces
c. london dispersion forces
Which of the following describes a reaction that is NEVER endergonic? a. negative enthalpy and negative entropy at high temperatures b. positive enthalpy and positive entropy at low temperatures c. negative enthalpy and positive entropy at high temperatures d. positive enthalpy and negative entropy at low temperatures
c. negative enthalpy and positive entropy at high temperatures
What will the H NMR spectrum of isobutane show? a. one 6 H triplet and one 4 H quartet b. two 3 H triplets and two 2 H quartets c. one 9 H doublet and one 1 H multiplet d. one 6 H, one 2 H multiplet, and one 2 H triplet
c. one 9 H doublet and one 1 H multiplet
As a substance goes from the gas phase to the solid phase, heat is: a. absorbed, internal energy decreases, and entropy decreases b. released, internal energy increases, and entropy decreases c. released, internal energy decreases, and entropy decreases d. released, internal energy decreases, and entropy increases
c. released, internal energy decreases, and entropy decreases
Which of the following accurately explains London dispersion forces? a. they exist only between partially charged molecules b. they are stronger than dipole-dipole interactions, but weaker than hydrogen bonding c. they are transient d. they are the main force responsible for keeping the antiparallel DNA strands together
c. they are transient
An atom contains 16 protons, 17 neutrons, and 18 electrons. Which of the following best indicates this ion? a. ³³Cl⁻ b. ³⁴Cl⁻ c. ³³S²⁻ d. ³⁴S²⁻
c. ³³S²⁻ any nucleus that contains 16 protons is sulfur. adding the protons and neutrons together gives a mass number of 33.
A 36 gram sample of water requires 93.4 kJ to sublime. What are the heats of fusion (∆Hfus) and vaporization (∆Hvap) for water? a. ∆Hfus= -20 kJ/mol, ∆Hvap= 66.7 kJ/mol b. ∆Hfus= 40.7 kJ/mol, ∆Hvap= 6.0 kJ/mol c. ∆Hfus= 6.0 kJ/mol, ∆Hvap= 40.7 kJ/mol d. ∆Hfus= 12.0 kJ/mol, ∆Hvap= 81.4 kJ/mol
c. ∆Hfus= 6.0 kJ/mol, ∆Hvap= 40.7 kJ/mol both fusion and vaporization require energy and are endothermic, eliminating choice A. vaporization takes substantially more energy. during vaporization, intermolecular forces are essentially completely overcome, and gaseous molecules separate widely due to their increased kinetic energy, eliminating choice B. a 36 gram sample of water is 2 moles, so the heat of sublimation of 1 mole is half of 93.4 kJ, or 46.7 kJ/mol which eliminates choice D
reduction occurs at the
cathode
current flow equation
charge x time
van der waals forces
collectively, dipole forces, hydrogen bonding, and london forces
aryl amines
compounds in which nitrogen is bonded to an sp2-hybridized carbon of an aromatic ring
alkyl amines
compounds in which nitrogen is bound to an sp3-hybridized carbon
column chromatography
compounds separate and leave the column in order from least polar to most polar due to reacting to the silica gel
conformational isomers
compounds that have the same molecular formula and the same atomic connectivity, but differ from one another by rotation about a sigma bond
constitutional isomers
compounds that have the same molecular formula but have their atoms connected together differently
electrolytic cell
consists of nonspontaneous reactions and requires an external electrical power source
alkene
contains a carbon-carbon double bond
alkyne
contains a carbon-carbon triple bond
disulfide bonds
contribute to tertiary or quaternary structure, but not primary or secondary
The average specific heat of the human body is 3470 J/kg x °C. If metabolism converts about 60% of energy to heat, how many joules of energy are consumed to raise the temperature of a 50kg body by 2°C? a. 34.7 kJ b. 57.8 kJ c. 347 kJ d. 578 kJ
d. 578 kJ the amount of heat required to raise anything to a certain temperature is given by the equation q=mc∆t. use this equation to find q, given m, c, and ∆t in the question stem. q= 50 kg(3470 J/kg x °C)(2°C)=347 x 10³ J=347 kJ since only 60% of the energy consumed is converted into heat, take 60% of 347 kJ. 347/0.6=578 kJ
Which of the following should have the highest enthalpy of vaporization? a. N₂ b. Br₂ c. Hg d. Al
d. Al enthalpy of vaporization is the heat energy required per mole to change from the liquid to gas phase. N₂ is a gas at room temperature, Br₂ and Hg are both liquids at room temperature, and Al is solid at room temperature. therefore, it is expected that Al will have the highest enthalpy of vaporization
Which of the following atoms/ions has electrons in the sub shell of highest energy? a. Cl- b. Ca²⁺ c. Cr⁺ d. As
d. As
Which one of the following anions cannot behave as a lewis base/ligand? a. F- b. OH- c. NO₃- d. BH₄-
d. BH₄- a lewis base/ligand is a molecule or ion that donates a pair of nonbonding electrons. so in order to even be a candidate lewis base/ligand, a molecule must have a pair of nonbonding electrons in the first place. choice D does not have any nonbonding electrons
Molecules that experience strong intermolecular forces tend to have high specific heats. Of the following molecules, which one is likely to have the highest specific heat? a. CH₄ b. (CH₃)₄Si c. CO d. CH₃OH
d. CH₃OH we are looking for the molecules with the strongest intermolecular forces. choices A and B are eliminated because these are non polar molecules that only experience weak London dispersion forces. methanol (choice D) is a better choice than C because methanol will experience hydrogen bonding while carbon monoxide experiences only weak dipole forces.
Of the following metallic elements, which as the lowest second ionization energy? a. Na b. K c. Mg d. Ca
d. Ca
In which of the following compounds is the mass percent of each of the constituent elements nearly identical? a. NaCl b. LiBr c. HCl d. CaF₂
d. CaF₂ calcium's molecular weight is 40.1 g/mol. the 2 flourines add up to almost 38.
Which of the following has the smallest atomic or ionic radius? a. Cl- b. Ar c. K⁺ d. Ca²⁺
d. Ca²⁺
Of the following, which is the strongest acid? a. H₂O b. H₂S c. HCl d. HBr
d. HBr acidity increases with increasing stability of the conjugate base. when comparing atoms in a period, those that are more electronegative are more stable and those that are larger are more stable
Which of the following is NOT an example of a Bohr atom? a. H b. He⁺ c. Li²⁺ d. H⁺
d. H⁺ a Bohr atom is one that contains only one electron. since H⁺ has a positive charge from the one electron in the neutral atom thereby having no electrons at all, choice D is the answer
Identify the mixture of compounds that cannot experience hydrogen bonding with each other: a. NH₃/H₂O b. H₂O/HF c. HF/CO₂ d. H₂S/HCl
d. H₂S/HCl hydrogen bonding occurs when an H covalently bonded to an F, O, or N electrostatically interacts with another F, O, or N. therefore A, B and C can all experience hydrogen bonding.
Functions of the integumentary system include: I. fighting against infection II. regulating body temperature III. regulating water movement a. I only b. I and II only c. II and III only d. I, II, and III
d. I, II, and III
Which of the following is/are true of germinal diols? I. germinal diols can only form on a terminal carbon II. they always contain two alcohol groups on the same carbon III. when made from carbonyls, the carbonyl carbon is electrophilic a. I only b. II only c. III only d. II and III only
d. II and III only
Which of the following is most likely an ionic compound? a. NO b. HI c. ClF d. KBr
d. KBr a diatomic compound is ionic if the electronegativities of the atoms are very different. of the choices listed, D has the greatest electronegativity difference.
Which atom has 3 unpaired electrons in its valence energy level? a. Li b. Be c. C d. N
d. N
Which of the following correctly describes a trend associated with effective nuclear charge (Zeff)? a. Zeff decreases as number of valence electrons increases b. Zeff increases as number of valence electrons decreases c. Zeff is positively correlated with atomic radius d. Zeff is negatively correlated with atomic radius
d. Zeff is negatively correlated with atomic radius
Chymotrypsin is synthesized by the pancreas in an inactive form, and undergoes a structural change when it is activated in the lumen of the small intestine. This is most clearly described as an example of: a. negative feedback b. positive feedback c. quaternary structure d. a zymogen
d. a zymogen
Which of the following is NOT a lipid derivative? a. waxes b. lipids c. carotenoids d. albumins
d. albumins
Given that each of the following solutions is at equilibrium with its environment, which solution should have the lowest temperature at 1 atm? a. a solution that is 1% ice and 99% liquid water b. a solution that is 50% ice and 50% liquid water c. a solution that is 99% ice and 1% liquid water d. all of these solutions will have the same temperature
d. all of these solutions will have the same temperature as long as there is any amount of ice and liquid water coexisting at equilibrium, the temperature must be 0°C at 1 atm.
Among the carboxylic acid derivatives, anhydrides are more reactive than amides. Which of the following best explains this phenomenon? a. anhydrides have more resonance structures that make the carbonyl carbon more nucleophilic b. amides have an animo group, which pulls electron density away from the carbonyl carbon, making it less reactive c. amides are smaller and have less steric hindrance d. anhydrides have 3 electron withdrawing oxygens that increases electrophilicity
d. anhydrides have 3 electron withdrawing oxygens that increases electrophilicity
Which of the following elements is diamagnetic? a. sodium b. sulfur c. potassium d. calcium
d. calcium a diamagnetic must have an even number of electrons and all must be spin paired
Of the following, which has the most negative electron affinity? a. barium b. bromine c. phosphorus d. chlorine
d. chlorine barium is in group II and therefore has a large positive electron affinity, so it can be eliminated. electron affinity values tend to become more negative as we go to the right across a row or up within a column, we'd expect chlorine to have the most negative electron affinity.
Tautomerization results in: a. enantiomers b. conformational isomers c. stereoisomers d. constitutional isomers
d. constitutional isomers
Where a cell membrane is myelinated, the capacitance of the membrane is: a. increased due to the excess of voltage-gated channels present on the cell membrane b. decreased due to the excess of voltage-gated channels present on the cell membrane c. increased because the myelin sheath increases the charge separation d. decreased because the myelin sheath increases the charge separation
d. decreased because the myelin sheath increases the charge separation the axon can be thought of as a parallel plate capacitor, with the cell membrane acting as an insulator between the relatively negative inside of the neuron and the relatively positive outside. because the presence of the myelin sheath increases the distance between these two "plates", capacitance is decreased.
Consider two electron transitions. In the first case, an electron falls from n=4 to n=2, giving off a photon of light with a wavelength equal to 488 nm. In the second transition, an electron moves from n=3 to n=4. For this transition, we would expect that: a. energy is emitted, and the wavelength of the corresponding photon will be shorter than the first transition b. energy is emitted, and the wavelength of the corresponding photon will be longer than the first transition c. energy is absorbed, and the wavelength of the corresponding photon will be shorter than the first transition d. energy is absorbed, and the wavelength of the corresponding photon will be longer than the first transition
d. energy is absorbed, and the wavelength of the corresponding photon will be longer than the first transition
Resonance structures are two or more structures where: a. only atoms may move around b. only bonding electrons may move around c. only nonbonding electrons may move around d. only nonbonding electrons, and double and triple bonds may move around
d. only nonbonding electrons, and double and triple bonds may move around
Which of the following types of bonds has the LEAST influence in determining the second/tertiary structures of a protein? a. hydrogen bonding b. hydrophobic interactions c. electrostatic interactions d. peptide bonds
d. peptide bonds peptide bonds link the primary sequence of amino acids in a protein, but they are never observed when a polypeptide bends or folds to form a secondary structure.
Which one of the following processes does NOT contribute to the change in enthalpy, ∆Hrxn, of a chemical reaction? a. phase change b. formation of stronger intermolecular forces c. breaking covalent bonds d. the presence of a heterogenous catalyst
d. the presence of a heterogenous catalyst
An atomic orbital around a central atom has 1/3 s character. What is the molecular geometry of the central atom? a. bent b. tetrahedral c. trigonal bipyramidal d. trigonal planar
d. trigonal planar
Radioactive calcium-47, a known beta- emitter, is administered in the form of ⁴⁷CaCl₂ by I.V. as a diagnostic tool to study calcium metabolism. What is the daughter nucleus of ⁴⁷Ca? a. ⁴⁶K b. ⁴⁷K c. ⁴⁷Ca⁺ d. ⁴⁷Sc
d. ⁴⁷Sc beta- decay will always change the identity of an element
geminal diols
diols with hydroxyl groups on the same carbon
arrhenius acids
dissociate in water to form hydrogen ions
arrhenius bases
dissociate in water to form hydroxide ions
solids
do not appear in Keq expressions
oxidation states
do not change upon protonation
acid base reactions
do not involve oxidation states
Determine the oxidation state of O₂
each O atom in has an oxidation state of 0 since it is in its standard state
Identify the lewis acid and the lewis base in the following reaction, which forms a coordination complex: 4 NH₃ + Zn²⁺ → Zn(NH₃)₄²⁺
each of the NH₃ molecules donates its lone pair to the zinc atom, thus forming four coordinate covalent bonds. since the zinc accepts these electron pairs, its the lewis acid. since each ammonia molecule donates an electron pair, they are lewis bases (or ligands)
when a substance absorbs or released heat, one of 2 things can happen:
either its temperature changes or it will undergo a phase change, but not both at the same time
lewis acid
electron pair acceptor
lewis base
electron pair donor
hund's rule
electrons in the same sub shell occupy abatable orbitals singly, before pairing up
aufbau principle
electrons occupy the lowest energy orbitals available
positive enthalpy
endothermic
anomers
epimers that form as a result of ring closure
london dispersion force
exists between temporary dipoles formed in non polar molecules as a result of a temporary asymmetric electron distribution
extraction of carboxylic acids
extraction with a dilute weak base - typically 5% sodium bicarbonate (NaHCO₃) - results in converting carboxylic acids into their corresponding anionic salts
frequency formula
f=1/T
covalent bond
formed between atoms when each contributes one or more of its unpaired valence electrons
grignard reagents
generally made via the action of an alkyl or acyl halide on magnesium metal
fluorine
has a -1 oxidation state
oxygen
has a -2 oxidation state
unsaturated
has at least one pi bond or a ring
particles in solution
has more entropy than undissolved solids
∆G°
has no affect on the rate of the reaction and vice versa
the value of ∆S for a reverse reaction
has the same magnitude as that of the forward reaction, but with opposite signs ∆Sreverse= -∆Sforward
group 1 metals
have a +1 oxidation state
group 2 metals
have a +2 oxidation state
halogens
have a -1 oxidation state
electrophiles
have a full or partial positive charge and love electrons, have an incomplete octet, also known as lewis acids
two moles of a substance
have more entropy than one mole
liquids
have more entropy than solids
gases
have more entropy than solids or liquids
ionic bonds
held together by the electrostatic attraction between a cation and anion
ionic solid
held together by the electrostatic attraction between cations and anions in a lattice structure
intermolecular intractions
hold matter together as solids or liquids
melting and boiling points are indicators of
how well identical molecules interact with each other
lipase
hydrolyzes fatty acids
zeroth law of thermodynamics
if 2 systems are both in thermal equilibrium with a third system, then the 2 initial systems are in thermal equilibrium with one another
hess's law
if a reaction occurs in several steps, then the sum of the energies absorbed or given off in all the steps will be the same as that for the overall reaction
paramagnetic
if an atom's electrons are not all spin-paired
liquid-liquid extraction
if the solution containing the compound of interest is shaken with a second solvent and allowed to separate into two distinct phased, the compound of interest will distribute itself between the two phases based
Diamond was a density of 3500 kg/m³. What is the volume, in cm³, of a 1 3/4-carat diamond (where, by definition, 1 carat=0.2 g)?
if we divide mass by density, we get volume, so converting 3500 kg/m³ into 3.5 g/cm³, we find that (1.75 x 0.2 g)/3.5 g/cm³=0.1 cm³
the solubility of gases in liquids tends to increase with
increasing pressure
the solubility of gases in liquids tends to decrease with
increasing temperature
the solubility of solids is liquids tends to increase with
increasing temperature
physical changes only affects
intermolecular forces between molecules or atoms (the attractive interactions between the molecules) and not intramolecular forces (the bonds between the atoms)
resistivity
inverse of conductivity
ionic compounds
involve the complete transfer of electrons
beta decay
involves the conversion of a neutron into a proton or vice versa
the amount of heat absorbed or released by a sample is proportional to
its change in temperature
ground state
lowest energy form of a molecule
lipids
mainly held together by london dispersion forces
energy is released in
making a bond
number of moles formula
mass in grams/molecular weight
gravitational potential energy
mass x gravity x height
density
mass/volume
q=
mc∆t q=heat added to or released by a sample m=mass of sample c=specific heat of the substance ∆t=temperature change
stereoisomers
molecules that have the same molecular formula and connectivity but differ from one another only in the spatial arrangement of the atoms
dipole dipole forces are experienced by
molecules with permanent dipoles, such as polar molecules
molarity
moles of solute per liter of solution
positive entropy
more disorder
gases
most energetic and least ordered of the phases
solids
most ordered and least energetic of the phases
carbanion
negatively charged
saturated
no pi bonds and no rings
non polar molecules are soluble in
non polar solvents
∆G > 0
non spontaneous in the forward direction
CH4
nonpolar
positive enthalpy, negative entropy
nonspontaneous at all temperatures
mole fraction
number of moles of substance/total number of moles in solution
esterification reaction
occurs when a carboxylic acid reacts with an alcohol in the presence of a catalytic amount of acid
how many sigma bonds are in a triple bond
one
methyl group
one carbon
conjugated system
one containing 3 or more atoms that each bear a p orbital
FAD
oxidizing agent
What is the formal charge on each atom in phosgene?
oxygen= 0 carbon= 0 chlorine= 0
simple distillation
performed when trace impurities need to be removed from a relatively pure compound or when a mixture of compounds with significantly different boiling points need to be separated
polar molecules are soluble in
polar solvents
Which has a greater formula weight: potassium dichromate (K₂Cr₂O₇) or lead azide Pb(N₃)₂?
potassium dichromate the formula weight of potassium dichromate is 294.2 the formula weight of lead azide is 291.2
one degree of unsaturation
presence of one pi bond or one ring
two degrees of unsaturation
presence of two pi bonds (two separate double bonds or one triple bind), or one pi bond and one ring, or two rings, and so on
bronsted lowry base
proton acceptor
bronsted lowry acid
proton donor
The melting point of iron is 1530°C, and its heat of fusion is 64 cal/g. How much heat would be required to completely melt a 50 g chunk of iron at 1530°C?
q=m∆Hfusion=(50 g)(64 cal/g)=3200 cal
the amount of heat accompanying a phase transition
q=n∆H n=number of moles of the substance ∆H=heat of phase change if ∆H and q are positive, heat is absorbed if ∆H and q are negative, heat is released
∆G = 0
reaction is at equilibrium
the conversion of a primary alcohol to an aldehyde
readily accomplished
the conversion of a secondary alcohol to a ketone
readily accomplished
the conversion of an aldehyde to a carboxylic acid
readily accomplished
tautomers
readily interconvertible constitutional isomers in equilibrium with one another
NADH
reducing agent
nucleophilic substitution reactions
replace a leaving group in an electrophilic substrate with a nucleophile
SN2 reaction
requires a good nucleophile
Which contains more formula units: a 1-mole sample of potassium dichromate (K₂Cr₂O₇) or a 1-mole sample of lead azide Pb(N₃)₂?
since both samples contain 1 mole, they both contain the same number of formula units
valence shell electron-pair repulsion (VSEPR) theory
since electrons repel one another, electron pairs, whether bonding or nonbonding, attempt to move as far apart as possible
sublimation
solid to gas
nucleophiles
species that have unshared pairs of electrons or pi bonds and frequently a negative charge, also known as lewis bases
negative enthalpy, positive entropy
spontaneous at all temperatures
positive enthalpy, positive entropy
spontaneous at high temperature
negative enthalpy, negative entropy
spontaneous at low temperature
∆G < 0
spontaneous in the forward direction
a galvanic cell
spontaneously generates electrical power
resonance effects
stabilize charge by delocalization through pi bonds
inductive effects
stabilize charge through sigma bonds
diastereomers
stereoisomers that are not enantiomers
alkene stretch (C=C)
strong and sharp around 1650
blood pressure reading
systolic/diastolic
radioactive decay
the altering of the number of ration of protons and neutrons to lower the energy of radioactive nuclei
the amount of chemical change is proportional to
the amount of electricity that flows through the cell
heat of transition (∆H)
the amount of energy required to complete a transition
standard heat of formation
the amount of energy required to make one mole of a compound from its constituent elements in their natural or standard state
heat of fusion
the amount of heat that must be absorbed to change solid into a liquid
salt bridge anions always migrate to
the anode
electrons always flow from
the anode to the cathode
dipole dipole forces
the attraction between the positive end of one polar molecule and the negative end of another polar molecule
resonance hybrid
the average of the different possible electron distributions of a molecule
cations always migrate to
the cathode
Inductive effects frequently alter the reactivity of molecules. Justify the fact that trichloroacetic acid (pKa=0.6) is a better acid than acetic acid (pKa=4.8)
the chlorine atoms in trichloroacetic acid are electron withdrawing. this decreases the amount of electron density elsewhere in the molecule, especially in the O-H bond. with less electron density, the O-H bond is weaker, making it more acidic than the O-H bond in acetic acid.
heat capacity
the constant of proportionality of a substance, which is the product of its specific heat
heat of vaporization
the energy absorbed when a liquid changes to a gas
What happens when energy flows out of a system into the surroundings?
the energy of the system decreases and the energy of the surroundings increases
What happens when energy flow into a system from the surroundings?
the energy of the system increases and the energy of the surroundings decreases
bond dissociation energy (BDE)
the energy required to break a bond homolytically
The mass defect of a helium nucleus is 5 x 10⁻²⁹ kg. What is its nuclear binding strength?
the equation E=(∆m)c² implies that 1 kg ↔ 9 x 10¹⁶ J so a mass defect of 5 x 10⁻²⁹ kg is equivalent to an energy of (5 x 10⁻²⁹ kg)(9 x 10¹⁶ J)=4.5 x 10⁻¹² J
the greater the concentration of reactants
the faster the reaction rate
the higher the temperature of the reaction mixture
the faster the reaction rate
the lower the activation energy
the faster the reaction rate
the higher the average kinetic energy of the molecules of a substance
the greater its entropy
the more hydrogen bond donors/acceptors in a compound
the higher the boiling and melting points will be
the sum of the oxidation states of the atoms in an ion must always equal
the ion's charge
racemization
the loss of defined stereochemistry and the mixture of R and S configurations
How many molecules of hydrazine, N₂H₄, are in a sample with a mass of 96 grams?
the molecular weight of hydrazine is 32, which means that 1 mole of N₂H₄ has a mass of 32 grams. a sample with 96 grams contains 3 moles of hydrazine molecules. 96 g/32 g/mol = 3 mols
determine the degree of unsaturation of the molecule: C₃H₈O
the molecule is saturated
the greater the intermolecular forces between molecules
the more energy will be required to get the compound to melt/boil
the greater the molecular weight of a compound
the more surface area there is to interact, the greater the number of van der waals interactions, and the higher the melting and boiling points
Determine the oxidation state of HNO₂
the oxidation state of H is +1, andO has an oxidation state of -2. N must have an oxidation of +3
Determine the oxidation state of NO₃⁻
the oxidation state of O is -2, making the oxidation state of N be +5
vapor pressure
the pressure exerted by the gaseous phase of a liquid that evaporated from the exposed surface of the liquid
Le Catelier's Principle
the principle stating that when equilibrium is disturbed the system will react to at least partially offset the disturbance
heisenberg's principle
the principle that one cannot simultaneously know the exact position and the exact momentum of an electron
distillation
the process of raising the temperature of a liquid until it can overcome the intermolecular forces that hold it together in the liquid phase. the vapor is then condensed back to the liquid phase and subsequently collected in another container
when a reaction is at equilibrium
the rate of the forward reaction is equal to the rate of the reverse reaction
distribution coefficient
the ratio of the substance's solubilities in the two solvents
limiting reagent
the reactant that runs out first
for similar bonds, the higher the bond order
the shorter and stronger the bond
empirical formula
the simplest positive integer ratio of atoms present in a compound
cathode
the site of reduction in a galvanic cell
the more positive the reduction potential
the stronger the reactant is an an oxidizing agent and the weaker the product is as a reducing agent
hydrogen bonding
the strongest dipole dipole force
formula weight
the sum of the atomic weights of all the atoms in the molecule
during a phase transition
the temperature of the substance does not change
half life
the time it takes for one half of some sample of the substance to decay
first law of thermodynamics
the total energy of the universe is constant
the more negative the reduction potential
the weaker the reactant is as an oxidizing agent and the stronger the product is as a reducing agent
if the cell voltage is negative
then the reaction is nonspontaneous
if the cell voltage is positive
then the reaction is spontaneous
pauli exclusion principle
there can be no more than 2 electrons in any given orbital
how many pi bonds are in a triple bond
two
atomic mass unit (amu)
unit for atomic weight
chromatography
used to separate mixtures of compounds, some for identification purposes and some for purification purposes
alpha particle
what a large nucleus emits when it wants to become more stable by reducing the number of protons and neutrons
molecule
when 2 or more atoms form a covalent bond
keto-enol tutomerism
when a ketone is converted into an enology by deprotonation of an alpha-carbon atom and subsequent protonation of the carbonyl oxygen
endothermic
when energy is absorbed into a system
exothermic
when energy is released from the system
butan-2-ol
when the position of the hydroxyl group needs to be specified, the number is placed after the name of the longest carbon chain and before the -ol suffix, separated by hyphens
meso compound
when theres an internal plane of symmetry in a molecule that contains chiral centers
dipole induced dipole force
where a permanent dipole in one molecules may induce a dipole in a neighboring non polar molecule, producing a momentary dipole induced dipole force
london dispersion forces
where an instantaneous dipole in a non polar molecule may induce a dipole in a neighboring non polar molecule
heterolytic bond cleavage
where both electrons of the electron pair that make up the bond end up on the same atom, forming a cation and an anion
homolytic blond cleavage
where on electron of the bond being broken goes to each fragment of the molecule
coordinate covalent bond
where one atom will donate both of the shared electrons in a bond
ion dipole forces
where polar molecules are attracted to ions
non polar bond
where the electron density between the two nuclei sharing electrons is even
polar bond
where the electron density between the two nuclei sharing the electrons is uneven, causing the molecule to have a dipole moment
one mol of an ideal gas at STP
will occupy a volume of 22.4 L
What can you predict if a carbonyl stretch is not present in IR spectroscopy?
you can eliminate compounds containing a carbonyl group, including aldehydes, ketones, carboxylic acids, acid chlorides, esters, amides, and anhydrides
change in entropy
∆S=Sproducts-Sreactants
