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Consider the reaction rate described by the following
equation.
Rate = k[A]m[B]n
The overall reaction is said to be second order when:
_
A
k is constant, m=0, and n=0.
B
k is constant, m=1, and n=1.
C
k is constant, m=2, and n=2.
D
k=2, and m and n are variable. - Correct Answers
✅Answer Key: B The reaction is second order if the sum
of the exponents m and n equals 2. In rate laws, k is the
rate constant. The sum of the exponents equals 2 when
m equals 1 and n equals 1. Thus, B is the correct answer.
A student plans to add HCl to a solution containing
Pb(NO3)2(aq). To determine how much Pb2+ will
precipitate from solution when the HCl is added, the
student needs to know which of the following?
_
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A
Ka for HCl
B
Ka for HNO3
C
Ksp for PbCl2
D
Keq for the reaction Pb2+ + 2 e- Pb - Correct Answers
✅Answer Key: C To determine how much Pb2+ will
precipitate, the student must know the solubility of PbCl2,
which is related to the solubility product constant Ksp of
PbCl2. Thus, C is the best answer.
Which of the following electron configurations of nitrogen
is the most stable?
_
A
1s22s12p4
B
1s22s22p3
C
1s12s22p4
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D
1s22s22p23s1 - Correct Answers ✅Answer Key: B The
atomic number of nitrogen is 7. The electrons will begin
to fill the lower energy levels first; consequently, the 1s
level will fill first with two electrons, followed by 2s with
two electrons, and then the 2p level with the last three
electrons. The resulting electron configuration is
1s22s22p3. Thus, B is the best answer.
When a weak acid (HA) is titrated with sodium hydroxide
in the presence of an indicator (HIn), the pH at which a
color change is observed depends on the:
_
A
final concentration of HA.
B
final concentration of HIn.
C
initial concentration of HA.
D
pKa of HIn. - Correct Answers ✅Answer Key: D The
indicator will change color over a specific pH range. The
range at which the color change takes place depends on
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the point at which HIn is converted to In-, and this
depends on the pKa of the indicator which is answer D.
Approximately how many moles of Al3+ are reduced
when 0.1 faraday of charge passes through a cell during
the production of Al? (Note: Assume there is excess Al3+
available and that Al3+ is reduced to Al metal only.)
_
A
0.033 mol
B
0.050 mol
C
0.067 mol
D
0.10 mol - Correct Answers ✅A faraday is equal to one
mole of electric charge. Because each aluminum ion
gains 3 electrons, 0.1 faraday of charge will reduce 0.1/3
moles of aluminum, or 0.033 moles of aluminum.
The following reaction occurs spontaneously.Cd(s) + 2 H+
(aq) → Cd2+(aq) + H2(g) Which of the following has the
highest electron affinity?
Prep Questions and Answers
(Rationales) Latest Update 2025
Consider the reaction rate described by the following
equation.
Rate = k[A]m[B]n
The overall reaction is said to be second order when:
_
A
k is constant, m=0, and n=0.
B
k is constant, m=1, and n=1.
C
k is constant, m=2, and n=2.
D
k=2, and m and n are variable. - Correct Answers
✅Answer Key: B The reaction is second order if the sum
of the exponents m and n equals 2. In rate laws, k is the
rate constant. The sum of the exponents equals 2 when
m equals 1 and n equals 1. Thus, B is the correct answer.
A student plans to add HCl to a solution containing
Pb(NO3)2(aq). To determine how much Pb2+ will
precipitate from solution when the HCl is added, the
student needs to know which of the following?
_
,MCAT Official Prep Hub - MCAT Official
Prep Questions and Answers
(Rationales) Latest Update 2025
A
Ka for HCl
B
Ka for HNO3
C
Ksp for PbCl2
D
Keq for the reaction Pb2+ + 2 e- Pb - Correct Answers
✅Answer Key: C To determine how much Pb2+ will
precipitate, the student must know the solubility of PbCl2,
which is related to the solubility product constant Ksp of
PbCl2. Thus, C is the best answer.
Which of the following electron configurations of nitrogen
is the most stable?
_
A
1s22s12p4
B
1s22s22p3
C
1s12s22p4
,MCAT Official Prep Hub - MCAT Official
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D
1s22s22p23s1 - Correct Answers ✅Answer Key: B The
atomic number of nitrogen is 7. The electrons will begin
to fill the lower energy levels first; consequently, the 1s
level will fill first with two electrons, followed by 2s with
two electrons, and then the 2p level with the last three
electrons. The resulting electron configuration is
1s22s22p3. Thus, B is the best answer.
When a weak acid (HA) is titrated with sodium hydroxide
in the presence of an indicator (HIn), the pH at which a
color change is observed depends on the:
_
A
final concentration of HA.
B
final concentration of HIn.
C
initial concentration of HA.
D
pKa of HIn. - Correct Answers ✅Answer Key: D The
indicator will change color over a specific pH range. The
range at which the color change takes place depends on
, MCAT Official Prep Hub - MCAT Official
Prep Questions and Answers
(Rationales) Latest Update 2025
the point at which HIn is converted to In-, and this
depends on the pKa of the indicator which is answer D.
Approximately how many moles of Al3+ are reduced
when 0.1 faraday of charge passes through a cell during
the production of Al? (Note: Assume there is excess Al3+
available and that Al3+ is reduced to Al metal only.)
_
A
0.033 mol
B
0.050 mol
C
0.067 mol
D
0.10 mol - Correct Answers ✅A faraday is equal to one
mole of electric charge. Because each aluminum ion
gains 3 electrons, 0.1 faraday of charge will reduce 0.1/3
moles of aluminum, or 0.033 moles of aluminum.
The following reaction occurs spontaneously.Cd(s) + 2 H+
(aq) → Cd2+(aq) + H2(g) Which of the following has the
highest electron affinity?
