MCAT Official Prep Practice Exam 3
with Accurate Solutions
An aldol addition occurs if there is no dehydration in an aldol condensation. The product
must be a _____, since the aldol condensation is not followed by a dehydration
reaction. - ANS-b-hydroxyketone.
Michael addition reaction - ANS-
Robinson annulation - ANS-
If the generator-brake system alone were engaged when the railcar was moving, which
of the following graphs would most accurately represent the subsequent speed of the
railcar?
Background: The speed of the car decreases in time such that the decelerating force
declines linearly with speed, according to the passage. - ANS-Because the decelerating
force is directly proportional to the deceleration acceleration, it follows that the
decelerating acceleration itself declines linearly with speed. Finally, because the
decelerating acceleration is rate of change of velocity, or the slope of the velocity vs.
time graph, then the slope of the graph must decrease in time.
Radioactive tritium (3H) labeled guanine has been used to measure the rate of
biochemical processes that involve its binding or incorporation.
Given that water is the solvent for this type of experiment, what is the best site for tritium
labeling?
I (the C between the two N atom on the five carbon ring)
II
III
IV - ANS-I
The best site for tritium labeling would not exchange the tritium ions for protons in water.
All of the N−H sites (II−IV) would readily exchange tritium protons due to their lone pair-
facilitating protonation and subsequent tritium exchange with water, but the C−H site (I),
lacking a lone pair, would retain its tritium label.
In its lowest-energy electron configuration, zinc has a: - ANS-filled 3d energy level and a
filled 4s energy level.
, Based on subshell filling rules, the 12 valence electrons occupy 4s and 3d subshells,
which are completely filled. Zn is element number 30 and in Group 12 of the Periodic
Table.
Iodine and zinc are the reactants in an experiment to find the stoichiometry of a
reaction. Gray, granular zinc metal (2.0 g) and purple iodine crystals (2.0 g) are added
to an Erlenmeyer flask containing 25 mL of methanol (CH3OH). The iodine dissolves in
the methanol giving a red-brown solution. After 15 min of heating, the solution is pale
yellow, and a few gray granules remain at the bottom of the flask. The liquid is decanted
into a beaker. The remaining granules are rinsed several times with methanol, and the
methanol from each rinse is added to the beaker. The methanol is then evaporated,
leaving a solid, yellow-white product of iodide of zinc. The mass of the dry product is
obtained. The unreacted zinc granules are also dried and weighed.
A 2:1 ratio of moles of iodine atoms to zinc atoms in the product is consistently
obtained. The mass of iodine and reacted zinc equals the mass of product. - ANS-...
What type of reaction is occurring between I2 and Zn? - ANS-oxidation reduction
Both zinc and iodine change oxidation states during the reaction
The glucose meter measures the current produced during Reaction 2. If 0.67 μmol of
electrons were measured, what mass of glucose was present in the sample? (Note: The
molar mass of glucose is 180 g/mol = 180 μg/μmol.)
Background: The stoichiometry of the reaction is 2 mol e- per mole of glucose
consumed. The device measured 0.67 (2/3) μmol of electrons. - ANS-60 ug
The stoichiometry of the reaction is 2 mol e- per mole of glucose consumed. The device
measured 0.67 (2/3) μmol of electrons, indicating that 0.33 (1/3) μmol of glucose was
consumed. This weighs 60 μg, based on its molar mass of 180 g/mol.
What additional substance is necessary for Reaction 2 to take place?
(D-Glucose --> D-gluconolactone)
FAD
NADH
H2O
Acetyl-CoA - ANS-FAD
An oxidizing agent is required for Reaction 2 to proceed. Of the choices listed, only FAD
is a cofactor oxidant.
The pH of a 1 L phosphate buffer solution was measured as 7.6, but the experimental
procedure calls for a pH 7.2 buffer. Which method will adjust the solution to the proper
with Accurate Solutions
An aldol addition occurs if there is no dehydration in an aldol condensation. The product
must be a _____, since the aldol condensation is not followed by a dehydration
reaction. - ANS-b-hydroxyketone.
Michael addition reaction - ANS-
Robinson annulation - ANS-
If the generator-brake system alone were engaged when the railcar was moving, which
of the following graphs would most accurately represent the subsequent speed of the
railcar?
Background: The speed of the car decreases in time such that the decelerating force
declines linearly with speed, according to the passage. - ANS-Because the decelerating
force is directly proportional to the deceleration acceleration, it follows that the
decelerating acceleration itself declines linearly with speed. Finally, because the
decelerating acceleration is rate of change of velocity, or the slope of the velocity vs.
time graph, then the slope of the graph must decrease in time.
Radioactive tritium (3H) labeled guanine has been used to measure the rate of
biochemical processes that involve its binding or incorporation.
Given that water is the solvent for this type of experiment, what is the best site for tritium
labeling?
I (the C between the two N atom on the five carbon ring)
II
III
IV - ANS-I
The best site for tritium labeling would not exchange the tritium ions for protons in water.
All of the N−H sites (II−IV) would readily exchange tritium protons due to their lone pair-
facilitating protonation and subsequent tritium exchange with water, but the C−H site (I),
lacking a lone pair, would retain its tritium label.
In its lowest-energy electron configuration, zinc has a: - ANS-filled 3d energy level and a
filled 4s energy level.
, Based on subshell filling rules, the 12 valence electrons occupy 4s and 3d subshells,
which are completely filled. Zn is element number 30 and in Group 12 of the Periodic
Table.
Iodine and zinc are the reactants in an experiment to find the stoichiometry of a
reaction. Gray, granular zinc metal (2.0 g) and purple iodine crystals (2.0 g) are added
to an Erlenmeyer flask containing 25 mL of methanol (CH3OH). The iodine dissolves in
the methanol giving a red-brown solution. After 15 min of heating, the solution is pale
yellow, and a few gray granules remain at the bottom of the flask. The liquid is decanted
into a beaker. The remaining granules are rinsed several times with methanol, and the
methanol from each rinse is added to the beaker. The methanol is then evaporated,
leaving a solid, yellow-white product of iodide of zinc. The mass of the dry product is
obtained. The unreacted zinc granules are also dried and weighed.
A 2:1 ratio of moles of iodine atoms to zinc atoms in the product is consistently
obtained. The mass of iodine and reacted zinc equals the mass of product. - ANS-...
What type of reaction is occurring between I2 and Zn? - ANS-oxidation reduction
Both zinc and iodine change oxidation states during the reaction
The glucose meter measures the current produced during Reaction 2. If 0.67 μmol of
electrons were measured, what mass of glucose was present in the sample? (Note: The
molar mass of glucose is 180 g/mol = 180 μg/μmol.)
Background: The stoichiometry of the reaction is 2 mol e- per mole of glucose
consumed. The device measured 0.67 (2/3) μmol of electrons. - ANS-60 ug
The stoichiometry of the reaction is 2 mol e- per mole of glucose consumed. The device
measured 0.67 (2/3) μmol of electrons, indicating that 0.33 (1/3) μmol of glucose was
consumed. This weighs 60 μg, based on its molar mass of 180 g/mol.
What additional substance is necessary for Reaction 2 to take place?
(D-Glucose --> D-gluconolactone)
FAD
NADH
H2O
Acetyl-CoA - ANS-FAD
An oxidizing agent is required for Reaction 2 to proceed. Of the choices listed, only FAD
is a cofactor oxidant.
The pH of a 1 L phosphate buffer solution was measured as 7.6, but the experimental
procedure calls for a pH 7.2 buffer. Which method will adjust the solution to the proper
