,CHEM 210 Module 2 Exam | Biochemistry |
Portage Learning | Q & A | 2026 Edition
1. What is the molecular shape of a water molecule?
A) Linear
B) Tetrahedral
C) Bent
D) Trigonal planar
Correct Answer: Bent
Rationale: A water molecule has a bent shape due to the two lone pairs of electrons on the oxygen
atom, which repel the bonding pairs and push them closer together. The bond angle is approximately
104.5 degrees.
2. The bond angle in a water molecule is approximately:
A) 90 degrees
B) 104.5 degrees
C) 109.5 degrees
D) 120 degrees
Correct Answer: 104.5 degrees
Rationale: The bond angle in water is 104.5 degrees, a consequence of its bent shape caused by the two
lone pairs of electrons on the oxygen atom.
3. Which of the following best defines autoionization?
A) The ability of a compound to react with itself to form ions
B) The process of a substance dissolving in water
C) The formation of a hydrogen bond
,D) The separation of a compound into its constituent elements
Correct Answer: The ability of a compound to react with itself to form ions
Rationale: Autoionization is the ability of a compound, like water, to react with itself to form ions. For
water, this process generates H₃O⁺ and OH⁻ ions.
4. What is the product of the autoionization constant of water, Kw?
A) 1.0 × 10⁻¹⁴
B) 1.0 × 10⁻⁷
C) 1.0 × 10⁺⁷
D) 1.0 × 10⁺¹⁴
Correct Answer: 1.0 × 10⁻¹⁴
Rationale: The autoionization constant for water, Kw, is 1.0 × 10⁻¹⁴ at 25°C. This constant is the product
of the concentrations of H⁺ and OH⁻ ions [Kw = (H⁺)(OH⁻)].
5. What is the hydrogen ion concentration [H⁺] of a solution with a pH of 5.0?
A) 1.0 × 10⁵ M
B) 1.0 × 10⁻⁵ M
C) 1.0 × 10⁻⁹ M
D) 1.0 × 10⁹ M
Correct Answer: 1.0 × 10⁻⁵ M
Rationale: The pH is the negative logarithm of the hydrogen ion concentration. A pH of 5.0 indicates [H⁺]
= 1.0 × 10⁻⁵ M.
6. What is the hydroxide ion concentration [OH⁻] of a solution with a pH of 5.0?
, A) 1.0 × 10⁻⁵ M
B) 1.0 × 10⁻⁹ M
C) 1.0 × 10⁵ M
D) 1.0 × 10⁹ M
Correct Answer: 1.0 × 10⁻⁹ M
Rationale: For any aqueous solution at 25°C, [H⁺][OH⁻] = 1.0 × 10⁻¹⁴. If [H⁺] = 1.0 × 10⁻⁵ M, then [OH⁻] =
1.0 × 10⁻⁹ M.
7. The pH of a solution of 0.0010 M NaOH is:
A) 1
B) 8
C) 11
D) 14
Correct Answer: 11
Rationale: NaOH is a strong base, so [OH⁻] = 0.0010 M. Using Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ gives [H⁺] = 1.0
× 10⁻¹¹ M. The pH is then -log(1.0 × 10⁻¹¹) = 11.
8. The pH of a solution of 8.9 × 10⁻¹² M NaOH is:
A) 8.9
B) 11
C) 4.8
D) 2.9
Correct Answer: 2.9
Portage Learning | Q & A | 2026 Edition
1. What is the molecular shape of a water molecule?
A) Linear
B) Tetrahedral
C) Bent
D) Trigonal planar
Correct Answer: Bent
Rationale: A water molecule has a bent shape due to the two lone pairs of electrons on the oxygen
atom, which repel the bonding pairs and push them closer together. The bond angle is approximately
104.5 degrees.
2. The bond angle in a water molecule is approximately:
A) 90 degrees
B) 104.5 degrees
C) 109.5 degrees
D) 120 degrees
Correct Answer: 104.5 degrees
Rationale: The bond angle in water is 104.5 degrees, a consequence of its bent shape caused by the two
lone pairs of electrons on the oxygen atom.
3. Which of the following best defines autoionization?
A) The ability of a compound to react with itself to form ions
B) The process of a substance dissolving in water
C) The formation of a hydrogen bond
,D) The separation of a compound into its constituent elements
Correct Answer: The ability of a compound to react with itself to form ions
Rationale: Autoionization is the ability of a compound, like water, to react with itself to form ions. For
water, this process generates H₃O⁺ and OH⁻ ions.
4. What is the product of the autoionization constant of water, Kw?
A) 1.0 × 10⁻¹⁴
B) 1.0 × 10⁻⁷
C) 1.0 × 10⁺⁷
D) 1.0 × 10⁺¹⁴
Correct Answer: 1.0 × 10⁻¹⁴
Rationale: The autoionization constant for water, Kw, is 1.0 × 10⁻¹⁴ at 25°C. This constant is the product
of the concentrations of H⁺ and OH⁻ ions [Kw = (H⁺)(OH⁻)].
5. What is the hydrogen ion concentration [H⁺] of a solution with a pH of 5.0?
A) 1.0 × 10⁵ M
B) 1.0 × 10⁻⁵ M
C) 1.0 × 10⁻⁹ M
D) 1.0 × 10⁹ M
Correct Answer: 1.0 × 10⁻⁵ M
Rationale: The pH is the negative logarithm of the hydrogen ion concentration. A pH of 5.0 indicates [H⁺]
= 1.0 × 10⁻⁵ M.
6. What is the hydroxide ion concentration [OH⁻] of a solution with a pH of 5.0?
, A) 1.0 × 10⁻⁵ M
B) 1.0 × 10⁻⁹ M
C) 1.0 × 10⁵ M
D) 1.0 × 10⁹ M
Correct Answer: 1.0 × 10⁻⁹ M
Rationale: For any aqueous solution at 25°C, [H⁺][OH⁻] = 1.0 × 10⁻¹⁴. If [H⁺] = 1.0 × 10⁻⁵ M, then [OH⁻] =
1.0 × 10⁻⁹ M.
7. The pH of a solution of 0.0010 M NaOH is:
A) 1
B) 8
C) 11
D) 14
Correct Answer: 11
Rationale: NaOH is a strong base, so [OH⁻] = 0.0010 M. Using Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ gives [H⁺] = 1.0
× 10⁻¹¹ M. The pH is then -log(1.0 × 10⁻¹¹) = 11.
8. The pH of a solution of 8.9 × 10⁻¹² M NaOH is:
A) 8.9
B) 11
C) 4.8
D) 2.9
Correct Answer: 2.9
