ACS GEN CHEM 2 EXAM / ACTUAL ACS GEN CHEM 2 FINAL EXAM
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1. For the reaction 2NO₂(g) → 2NO(g) + O₂(g), the rate law is rate = k[NO₂]². If
the concentration of NO₂ is doubled, the reaction rate will:
A) increase by a factor of 2
B) increase by a factor of 4
C) increase by a factor of 8
D) remain unchanged
B) increase by a factor of 4 (CORRECT ANSWER)
Rationale: The rate law is second order in NO₂. Doubling [NO₂] increases rate by
(2)² = 4 times. Options A, C, and D do not follow the squared dependence.
2. The half-life of a first-order reaction is 30 s. How much time is required for the
concentration to decrease from 0.80 M to 0.10 M?
A) 30 s
B) 60 s
C) 90 s
D) 120 s
C) 90 s (CORRECT ANSWER)
Rationale: For first order, each half-life halves concentration. 0.80 → 0.40 (1 half-
life, 30 s), 0.40 → 0.20 (2nd, 60 s total), 0.20 → 0.10 (3rd, 90 s total). Thus 3 half-
lives = 90 s.
,3. Which factor does NOT affect the rate of a chemical reaction?
A) Temperature
B) Concentration of reactants
C) Activation energy
D) ΔG° of the reaction
D) ΔG° of the reaction (CORRECT ANSWER)
Rationale: ΔG° determines spontaneity, not rate. Temperature, concentration, and
activation energy (via catalyst or inherent barrier) affect rate. ΔG° is
thermodynamic, not kinetic.
4. (Revised) For the endothermic reaction N₂(g) + O₂(g) ⇌ 2NO(g), which change
would shift the equilibrium to the left?
A) Increasing pressure
B) Decreasing temperature
C) Adding N₂
D) Removing NO
B) Decreasing temperature (CORRECT ANSWER)
Rationale: Endothermic: heat is a reactant. Decreasing temperature removes heat,
shifting left (toward reactants). Increasing pressure favors fewer moles (right,
2→2? Actually same moles, no shift). Adding N₂ shifts right. Removing NO shifts
right.
,5. The equilibrium constant Kc for the reaction H₂(g) + I₂(g) ⇌ 2HI(g) is 54.3 at
430°C. If the initial concentrations are [H₂]=0.100 M, [I₂]=0.100 M, and [HI]=0 M,
what is the equilibrium concentration of HI?
A) 0.078 M
B) 0.156 M
C) 0.200 M
D) 0.312 M
B) 0.156 M (CORRECT ANSWER)
Rationale: ICE table: H₂ + I₂ ⇌ 2HI. Initial 0.1,0.1,0. Change -x, -x, +2x.
Equilibrium: 0.1-x, 0.1-x, 2x. Kc = (2x)²/(0.1-x)² = 54.3. Take sqrt: 2x/(0.1-
x)=7.37. Solve: 2x=0.737-7.37x → 9.37x=0.737 → x=0.0787. [HI]=2x=0.1574 M
≈0.156 M.
6. For a reaction with ΔH° = +50 kJ and ΔS° = +100 J/K at 298 K, which statement
is true?
A) Spontaneous at all temperatures
B) Spontaneous only at high temperatures
C) Spontaneous only at low temperatures
D) Non-spontaneous at all temperatures
B) Spontaneous only at high temperatures (CORRECT ANSWER)
Rationale: ΔG = ΔH - TΔS. ΔH>0, ΔS>0. At low T, ΔG>0 (non-spontaneous). At
high T, TΔS > ΔH, ΔG<0 (spontaneous). Thus spontaneous only at high T.
7. The pH of a 0.050 M solution of a weak acid (HA) is 2.80. What is the Ka of the
acid?
A) 1.0 × 10⁻⁵
, B) 2.5 × 10⁻⁵
C) 5.0 × 10⁻⁵
D) 1.0 × 10⁻⁴
C) 5.0 × 10⁻⁵ (CORRECT ANSWER)
Rationale: [H⁺]=10⁻²·⁸⁰=1.58×10⁻³ M. Approx: Ka=(1.58e-3)²/0.050=2.50e-
6/0.05=5.0e-5. Exact gives same within rounding.
8. Which of the following is a Brønsted-Lowry base but not an Arrhenius base?
A) NaOH
B) NH₃
C) Ca(OH)₂
D) KOH
B) NH₃ (CORRECT ANSWER)
Rationale: Arrhenius base releases OH⁻ in water. NH₃ accepts H⁺ but does not
directly release OH⁻; it produces OH⁻ by reacting with water: NH₃ + H₂O ⇌ NH₄⁺
+ OH⁻, so it is a Brønsted base but not an Arrhenius base (though some consider it
Arrhenius because it yields OH⁻ indirectly, but traditionally Arrhenius bases are
metal hydroxides). The distinction is clear: NH₃ is the classic example of a
Brønsted-Lowry base that is not an Arrhenius base.
9. The conjugate acid of HPO₄²⁻ is:
A) H₂PO₄⁻
B) PO₄³⁻
C) H₃PO₄
D) H₂O
LATEST 2026/2027 TESTBANK & STUDY GUIDE COMPLETE ACCURATE
EXAM APPROVED QUESTIONS AND CORRECT DETAILED ANSWERS
WITH RATIONALES (100% CORRECT VERIFIED ANSWERS) CURRENTLY
UPDATED VERSION 2026 EDITION |GUARANTEED PASS A+ (BRAND
NEW!) |JUST RELEASED |ACS GEN CHEM 2 FINAL
1. For the reaction 2NO₂(g) → 2NO(g) + O₂(g), the rate law is rate = k[NO₂]². If
the concentration of NO₂ is doubled, the reaction rate will:
A) increase by a factor of 2
B) increase by a factor of 4
C) increase by a factor of 8
D) remain unchanged
B) increase by a factor of 4 (CORRECT ANSWER)
Rationale: The rate law is second order in NO₂. Doubling [NO₂] increases rate by
(2)² = 4 times. Options A, C, and D do not follow the squared dependence.
2. The half-life of a first-order reaction is 30 s. How much time is required for the
concentration to decrease from 0.80 M to 0.10 M?
A) 30 s
B) 60 s
C) 90 s
D) 120 s
C) 90 s (CORRECT ANSWER)
Rationale: For first order, each half-life halves concentration. 0.80 → 0.40 (1 half-
life, 30 s), 0.40 → 0.20 (2nd, 60 s total), 0.20 → 0.10 (3rd, 90 s total). Thus 3 half-
lives = 90 s.
,3. Which factor does NOT affect the rate of a chemical reaction?
A) Temperature
B) Concentration of reactants
C) Activation energy
D) ΔG° of the reaction
D) ΔG° of the reaction (CORRECT ANSWER)
Rationale: ΔG° determines spontaneity, not rate. Temperature, concentration, and
activation energy (via catalyst or inherent barrier) affect rate. ΔG° is
thermodynamic, not kinetic.
4. (Revised) For the endothermic reaction N₂(g) + O₂(g) ⇌ 2NO(g), which change
would shift the equilibrium to the left?
A) Increasing pressure
B) Decreasing temperature
C) Adding N₂
D) Removing NO
B) Decreasing temperature (CORRECT ANSWER)
Rationale: Endothermic: heat is a reactant. Decreasing temperature removes heat,
shifting left (toward reactants). Increasing pressure favors fewer moles (right,
2→2? Actually same moles, no shift). Adding N₂ shifts right. Removing NO shifts
right.
,5. The equilibrium constant Kc for the reaction H₂(g) + I₂(g) ⇌ 2HI(g) is 54.3 at
430°C. If the initial concentrations are [H₂]=0.100 M, [I₂]=0.100 M, and [HI]=0 M,
what is the equilibrium concentration of HI?
A) 0.078 M
B) 0.156 M
C) 0.200 M
D) 0.312 M
B) 0.156 M (CORRECT ANSWER)
Rationale: ICE table: H₂ + I₂ ⇌ 2HI. Initial 0.1,0.1,0. Change -x, -x, +2x.
Equilibrium: 0.1-x, 0.1-x, 2x. Kc = (2x)²/(0.1-x)² = 54.3. Take sqrt: 2x/(0.1-
x)=7.37. Solve: 2x=0.737-7.37x → 9.37x=0.737 → x=0.0787. [HI]=2x=0.1574 M
≈0.156 M.
6. For a reaction with ΔH° = +50 kJ and ΔS° = +100 J/K at 298 K, which statement
is true?
A) Spontaneous at all temperatures
B) Spontaneous only at high temperatures
C) Spontaneous only at low temperatures
D) Non-spontaneous at all temperatures
B) Spontaneous only at high temperatures (CORRECT ANSWER)
Rationale: ΔG = ΔH - TΔS. ΔH>0, ΔS>0. At low T, ΔG>0 (non-spontaneous). At
high T, TΔS > ΔH, ΔG<0 (spontaneous). Thus spontaneous only at high T.
7. The pH of a 0.050 M solution of a weak acid (HA) is 2.80. What is the Ka of the
acid?
A) 1.0 × 10⁻⁵
, B) 2.5 × 10⁻⁵
C) 5.0 × 10⁻⁵
D) 1.0 × 10⁻⁴
C) 5.0 × 10⁻⁵ (CORRECT ANSWER)
Rationale: [H⁺]=10⁻²·⁸⁰=1.58×10⁻³ M. Approx: Ka=(1.58e-3)²/0.050=2.50e-
6/0.05=5.0e-5. Exact gives same within rounding.
8. Which of the following is a Brønsted-Lowry base but not an Arrhenius base?
A) NaOH
B) NH₃
C) Ca(OH)₂
D) KOH
B) NH₃ (CORRECT ANSWER)
Rationale: Arrhenius base releases OH⁻ in water. NH₃ accepts H⁺ but does not
directly release OH⁻; it produces OH⁻ by reacting with water: NH₃ + H₂O ⇌ NH₄⁺
+ OH⁻, so it is a Brønsted base but not an Arrhenius base (though some consider it
Arrhenius because it yields OH⁻ indirectly, but traditionally Arrhenius bases are
metal hydroxides). The distinction is clear: NH₃ is the classic example of a
Brønsted-Lowry base that is not an Arrhenius base.
9. The conjugate acid of HPO₄²⁻ is:
A) H₂PO₄⁻
B) PO₄³⁻
C) H₃PO₄
D) H₂O
