AAMC MCAT Practice 2023 Exam 1
In the chromatography of the reaction mixture, water absorbed on cellulose functioned
as the stationary phase. What was the principal factor determining the migration of
individual components in the sample?
A) Hydrogen bonding
B) Solute concentration
C) Stationary phase concentration
D) Thickness of paper - ANSWER A) Hydrogen bonding
The answer to this question is A because the relative amount of hydrogen bonding to the
stationary phase will determine the relative rate of migration of the various components
in the sample.
What assumption is being made if scientists conclude that aspartic acid was formed by
the prebiological synthesis in the passage?
A) Aspartic acid is unstable at temperatures below 150 degrees C.
B) All of the malic acid underwent the dehydration reaction to form fumaric/maleic acid.
C) Compound A and cyanide were available on primitive Earth.
D) The reaction between ammonia and fumaric acid was catalyzed by the presence of
water. - ANSWER C) Compound A and cyanide were available on primitive Earth.
he answer to this question is C since, in order for the experimental reaction sequence to
be relevant to the primordial formation of aspartic acid, the starting materials used
(Compound A and cyanide) are assumed to have been available.
According to the developed chromatography plate shown below, what is the
approximate Rf value of aspartic acid?
aspartic acid = 2
solvent front = 10
A) 0.20
B) 0.50
C) 5
,D) 10 - ANSWER The answer to this question is A (0.20) because Rf is the ratio of the
distance travelled by the analyte relative to the solvent front during a chromatographic
separation. Aspartic acid travelled two units, while the solvent front travelled ten units,
giving an Rf of 2/10 = 0.20 for aspartic acid.
Which of the following statements does NOT correctly describe the dehydration of malic
acid to fumaric acid and maleic acid?
A) The reaction occurs most readily with tertiary alcohols.
B) The reaction involves the loss of a water molecule.
C) The reaction has a carbocation intermediate.
D) The reaction is stereospecific. - ANSWER D) The reaction is stereospecific.
The answer to this question is D because the fact that both fumaric and maleic acid are
produced means that the dehydration of malic acid is NOT stereospecific.
What type of functional group is formed when aspartic acid reacts with another amino
acid to form a peptide bond?
A) An amine group
B) An aldehyde group
C) An amide group
D) A carboxyl group - ANSWER C) An amide group
The answer to this question is C because the functional group that forms during peptide
bond formation is known as an amide group.
If 2-pentanol replaces 1-pentanol in the reaction shown in Figure 3 (SN2), the rate of
substitution is less because:
A) the C-O bond in 2-pentanol is stronger than the C-O bond in 1-pentanol.
B) there is a competing elimination reaction that slows the rate of substitution.
C) there is more steric hindrance at the oxygen atom in 2-pentanol than in 1-pentanol,
making protonation less likely.
D) there is more steric hindrance at the 2-position of 2-pentanol than at the 1-position of
1-pentanol. - ANSWER D) there is more steric hindrance at the 2-position of 2-pentanol
than at the 1-position of 1-pentanol.
The answer to this question is D because the rate of substitution of protonated alcohols
,is subject to steric hindrance. This inhibits the ability of nucleophiles to collide with the
reacting electrophilic center and slows the rate of reaction.
If a solution containing the compounds shown in Figure 4, is injected into a gas-liquid
chromatograph, the first peak observed in the gc trace is attributable to which
compound?
A) Methyl-2-butanol
B) Methyl-2-butene
C) Chloro-2-methylbutane
D) Bromo-2-mehtylbutane - ANSWER B) Methyl-2-butene
The answer to this question is B because 2-methyl-2-butene will exhibit the lowest
molecular weight and also the weakest intermolecular forces of attraction. This
substance will therefore migrate the fastest and be the first peak in the gas
chromatograph (gc) trace.
R vs. S stereochemistry* - ANSWER R = clockwise
C = counter-clockwise
Acetic acid and ethanol react to form an ester product as shown below.
In determining which reactant loses the -OH group, which of the following isotopic
substitutions would be most useful?
A) Replace the acidic H of acetic acid with D
B) Replace the alcoholic H of ethanol with D.
C) Replace the carbonyl oxygen of acetic acid with O-18.
D) Replace the hydroxyl oxygen of ethanol with O-18. - ANSWER D) Replace the
hydroxyl oxygen of ethanol with O-18.
The answer to this question is D because this experiment involves labeling a group
which does not exchange with other groups present prior to reaction and will therefore
give information about the true identity of the groups, which are exchanged during the
reaction.
A person whose eye has a lens-to-retina distance of 2.0 cm, can only clearly see objects
that are closer than 1.0 m away. What is the strength S of the person's eye lens? (Note:
Use the thin lens formula 1/O + 1/I = S)
A) -50 D
, B) -10 D
C) 51 D
D) 55 D - ANSWER C) 51 D
The answer to this question is C because the strength of the eye lens is equal to the
inverse of the focal length of the eye lens. Its numerical value is given by (1 m)-1+(0.02
m)-1=1 D+50 D=51 D.
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. - ANSWER D) the
transition state changes the activation energy of the reaction.
The answer is D because the stabilization of the transition state, not the substrate,
provides binding energy that is used to lower the activation energy.
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 - ANSWER C) Adding concentrated HCl (aq)
The answer to this question is C because HCl is a strong acid that will increase the
amount of H+ in solution and thus decrease the percentage of CH3CO2H that ionizes.
When the current in the micro-robot's circuit increases and the resistance of the circuit
remains constant, the voltage of the circuit:
A) decreases
B) increases
C) is constant
D) is zero - ANSWER B) increases
In the chromatography of the reaction mixture, water absorbed on cellulose functioned
as the stationary phase. What was the principal factor determining the migration of
individual components in the sample?
A) Hydrogen bonding
B) Solute concentration
C) Stationary phase concentration
D) Thickness of paper - ANSWER A) Hydrogen bonding
The answer to this question is A because the relative amount of hydrogen bonding to the
stationary phase will determine the relative rate of migration of the various components
in the sample.
What assumption is being made if scientists conclude that aspartic acid was formed by
the prebiological synthesis in the passage?
A) Aspartic acid is unstable at temperatures below 150 degrees C.
B) All of the malic acid underwent the dehydration reaction to form fumaric/maleic acid.
C) Compound A and cyanide were available on primitive Earth.
D) The reaction between ammonia and fumaric acid was catalyzed by the presence of
water. - ANSWER C) Compound A and cyanide were available on primitive Earth.
he answer to this question is C since, in order for the experimental reaction sequence to
be relevant to the primordial formation of aspartic acid, the starting materials used
(Compound A and cyanide) are assumed to have been available.
According to the developed chromatography plate shown below, what is the
approximate Rf value of aspartic acid?
aspartic acid = 2
solvent front = 10
A) 0.20
B) 0.50
C) 5
,D) 10 - ANSWER The answer to this question is A (0.20) because Rf is the ratio of the
distance travelled by the analyte relative to the solvent front during a chromatographic
separation. Aspartic acid travelled two units, while the solvent front travelled ten units,
giving an Rf of 2/10 = 0.20 for aspartic acid.
Which of the following statements does NOT correctly describe the dehydration of malic
acid to fumaric acid and maleic acid?
A) The reaction occurs most readily with tertiary alcohols.
B) The reaction involves the loss of a water molecule.
C) The reaction has a carbocation intermediate.
D) The reaction is stereospecific. - ANSWER D) The reaction is stereospecific.
The answer to this question is D because the fact that both fumaric and maleic acid are
produced means that the dehydration of malic acid is NOT stereospecific.
What type of functional group is formed when aspartic acid reacts with another amino
acid to form a peptide bond?
A) An amine group
B) An aldehyde group
C) An amide group
D) A carboxyl group - ANSWER C) An amide group
The answer to this question is C because the functional group that forms during peptide
bond formation is known as an amide group.
If 2-pentanol replaces 1-pentanol in the reaction shown in Figure 3 (SN2), the rate of
substitution is less because:
A) the C-O bond in 2-pentanol is stronger than the C-O bond in 1-pentanol.
B) there is a competing elimination reaction that slows the rate of substitution.
C) there is more steric hindrance at the oxygen atom in 2-pentanol than in 1-pentanol,
making protonation less likely.
D) there is more steric hindrance at the 2-position of 2-pentanol than at the 1-position of
1-pentanol. - ANSWER D) there is more steric hindrance at the 2-position of 2-pentanol
than at the 1-position of 1-pentanol.
The answer to this question is D because the rate of substitution of protonated alcohols
,is subject to steric hindrance. This inhibits the ability of nucleophiles to collide with the
reacting electrophilic center and slows the rate of reaction.
If a solution containing the compounds shown in Figure 4, is injected into a gas-liquid
chromatograph, the first peak observed in the gc trace is attributable to which
compound?
A) Methyl-2-butanol
B) Methyl-2-butene
C) Chloro-2-methylbutane
D) Bromo-2-mehtylbutane - ANSWER B) Methyl-2-butene
The answer to this question is B because 2-methyl-2-butene will exhibit the lowest
molecular weight and also the weakest intermolecular forces of attraction. This
substance will therefore migrate the fastest and be the first peak in the gas
chromatograph (gc) trace.
R vs. S stereochemistry* - ANSWER R = clockwise
C = counter-clockwise
Acetic acid and ethanol react to form an ester product as shown below.
In determining which reactant loses the -OH group, which of the following isotopic
substitutions would be most useful?
A) Replace the acidic H of acetic acid with D
B) Replace the alcoholic H of ethanol with D.
C) Replace the carbonyl oxygen of acetic acid with O-18.
D) Replace the hydroxyl oxygen of ethanol with O-18. - ANSWER D) Replace the
hydroxyl oxygen of ethanol with O-18.
The answer to this question is D because this experiment involves labeling a group
which does not exchange with other groups present prior to reaction and will therefore
give information about the true identity of the groups, which are exchanged during the
reaction.
A person whose eye has a lens-to-retina distance of 2.0 cm, can only clearly see objects
that are closer than 1.0 m away. What is the strength S of the person's eye lens? (Note:
Use the thin lens formula 1/O + 1/I = S)
A) -50 D
, B) -10 D
C) 51 D
D) 55 D - ANSWER C) 51 D
The answer to this question is C because the strength of the eye lens is equal to the
inverse of the focal length of the eye lens. Its numerical value is given by (1 m)-1+(0.02
m)-1=1 D+50 D=51 D.
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. - ANSWER D) the
transition state changes the activation energy of the reaction.
The answer is D because the stabilization of the transition state, not the substrate,
provides binding energy that is used to lower the activation energy.
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 - ANSWER C) Adding concentrated HCl (aq)
The answer to this question is C because HCl is a strong acid that will increase the
amount of H+ in solution and thus decrease the percentage of CH3CO2H that ionizes.
When the current in the micro-robot's circuit increases and the resistance of the circuit
remains constant, the voltage of the circuit:
A) decreases
B) increases
C) is constant
D) is zero - ANSWER B) increases
