CHEM 104 MODULE 9 PRACTICE EXAM
QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2025
1. Which of the following is a strong acid?
A. HCl
B. HF
C. H₂CO₃
D. CH₃COOH
HCl fully dissociates in water, making it a strong acid.
2. Which of the following is a weak base?
A. NH₃
B. NaOH
C. KOH
D. Ca(OH)₂
Ammonia (NH₃) does not completely dissociate in water, so it is a weak base.
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,3. What is the pH of a solution with [H⁺] = 1 × 10⁻³ M?
A. 1
B. 2
C. 3
D. 4
pH = -log[H⁺] = -log(1 × 10⁻³) = 3.
4. A buffer solution:
A. Changes pH drastically
B. Is made only of strong acids
C. Resists changes in pH
D. Has no acid or base
Buffers maintain pH by neutralizing added acids or bases.
5. What is the conjugate base of H₂SO₄?
A. H₂SO₄⁻
B. HSO₄⁻
C. SO₄²⁻
D. OH⁻
When H₂SO₄ donates a proton, it forms HSO₄⁻.
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, 6. A solution with a pOH of 5 has a pH of:
A. 5
B. 9
C. 7
D. 14
pH + pOH = 14 → pH = 14 - 5 = 9.
7. Which acid is triprotic?
A. HCl
B. HNO₃
C. H₃PO₄
D. CH₃COOH
H₃PO₄ has three ionizable protons.
8. What is the Kw at 25°C?
A. 1 × 10⁻¹²
B. 1 × 10⁻¹⁴
C. 1 × 10⁻⁷
D. 1 × 10⁻¹⁰
Kw = [H⁺][OH⁻] = 1 × 10⁻¹⁴ at 25°C.
9. The conjugate acid of NH₃ is:
A. NH₄⁻
B. NH₄⁺
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QUESTIONS AND CORRECT ANSWERS
(VERIFIED ANSWERS) PLUS RATIONALES
2025
1. Which of the following is a strong acid?
A. HCl
B. HF
C. H₂CO₃
D. CH₃COOH
HCl fully dissociates in water, making it a strong acid.
2. Which of the following is a weak base?
A. NH₃
B. NaOH
C. KOH
D. Ca(OH)₂
Ammonia (NH₃) does not completely dissociate in water, so it is a weak base.
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,3. What is the pH of a solution with [H⁺] = 1 × 10⁻³ M?
A. 1
B. 2
C. 3
D. 4
pH = -log[H⁺] = -log(1 × 10⁻³) = 3.
4. A buffer solution:
A. Changes pH drastically
B. Is made only of strong acids
C. Resists changes in pH
D. Has no acid or base
Buffers maintain pH by neutralizing added acids or bases.
5. What is the conjugate base of H₂SO₄?
A. H₂SO₄⁻
B. HSO₄⁻
C. SO₄²⁻
D. OH⁻
When H₂SO₄ donates a proton, it forms HSO₄⁻.
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, 6. A solution with a pOH of 5 has a pH of:
A. 5
B. 9
C. 7
D. 14
pH + pOH = 14 → pH = 14 - 5 = 9.
7. Which acid is triprotic?
A. HCl
B. HNO₃
C. H₃PO₄
D. CH₃COOH
H₃PO₄ has three ionizable protons.
8. What is the Kw at 25°C?
A. 1 × 10⁻¹²
B. 1 × 10⁻¹⁴
C. 1 × 10⁻⁷
D. 1 × 10⁻¹⁰
Kw = [H⁺][OH⁻] = 1 × 10⁻¹⁴ at 25°C.
9. The conjugate acid of NH₃ is:
A. NH₄⁻
B. NH₄⁺
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