AAMC MCAT Practice Exam 1 Question and answers rated A+

AAMC MCAT Practice Exam 1 Question and answers rated A+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 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. 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 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. 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 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. 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 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* R = clockwise C = counter-clockwise