AAMC MCAT Practice Exam 1 Questions and Correct Answers

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 - 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. - 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 - 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 - B) increases V = IR The answer to this question is B because according to Ohm's law, current is equal to voltage divided by resistance. If current increases and resistance is constant, then voltage increases as well. 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 n = c/v The answer to this question is B because the index of refraction of a medium is equal to the ratio of the speed of light in vacuum to the speed of light in the medium, thus it is equal to (3.0 x 108 m/s)/(2.1 x 108 m/s) = 1.4. 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.