WGU C785 BIOCHEMISTRY EXAM PRACTICE TEST | 300 REAL EXAM
VERIFIED QUESTIONS AND ANSWERS WITH RATIONALES -
COMPREHENSIVE LATEST VERSION 2026/2027
(PASS GUARANTEE)
SECTION 1 – WATER, pH, AND BUFFERS (Questions 1–30)
Question 1
Which property of water allows it to act as a universal solvent for polar
substances?
A) High specific heat
B) Cohesion and adhesion
C) Polarity and hydrogen bonding
D) High surface tension
Answer: C
Rationale: Water's polarity and ability to form hydrogen bonds allow it to dissolve
polar and ionic substances. The partial charges interact with solutes.
Question 2
What is the pH of a solution with a hydrogen ion concentration of 1 × 10⁻⁴ M?
A) 2
B) 4
C) 6
D) 8
Answer: B
Rationale: pH = -log[H⁺]. For [H⁺] = 1 × 10⁻⁴, pH = 4.
Question 3
A buffer resists changes in pH by:
A) Absorbing all hydrogen ions
B) Releasing or accepting protons (H⁺)
C) Changing temperature
1
,D) Precipitating out of solution
Answer: B
Rationale: Buffers consist of a weak acid and its conjugate base. They release H⁺
when pH rises and accept H⁺ when pH falls.
Question 4
Which equation is used to calculate the pH of a buffer solution?
A) Michaelis-Menten equation
B) Henderson-Hasselbalch equation
C) Nernst equation
D) Arrhenius equation
Answer: B
Rationale: pH = pKa + log([A⁻]/[HA]) is the Henderson-Hasselbalch equation for
buffer pH.
Question 5
What is the pKa of an acid if the ratio of conjugate base to acid is 10:1 at pH 6?
A) 4
B) 5
C) 6
D) 7
Answer: B
Rationale: pH = pKa + log(10/1) = pKa + 1. If pH = 6, then pKa = 5.
Question 6
The bicarbonate buffer system is important for maintaining:
A) Intracellular pH only
B) Blood pH
C) Stomach acid
D) Urine pH
2
,Answer: B
Rationale: The HCO₃⁻/H₂CO₃ system is the primary blood buffer, maintaining pH
around 7.4.
Question 7
Which of the following is a strong acid?
A) Acetic acid
B) Carbonic acid
C) Hydrochloric acid
D) Phosphoric acid
Answer: C
Rationale: HCl dissociates completely in water, making it a strong acid. The others
are weak acids.
Question 8
The auto-ionization of water produces:
A) H⁺ and OH⁻
B) H₂ and O₂
C) Na⁺ and Cl⁻
D) H₂O₂
Answer: A
Rationale: 2H₂O ⇌ H₃O⁺ + OH⁻ (simplified as H⁺ and OH⁻).
Question 9
A solution with pH 3 is how many times more acidic than a solution with pH 5?
A) 2
B) 10
C) 100
D) 1000
3
, Answer: C
Rationale: Each pH unit represents a 10-fold change. pH 3 vs pH 5 is 10² = 100
times more acidic.
Question 10
What is the [OH⁻] in a solution with pH 10?
A) 1 × 10⁻¹⁰ M
B) 1 × 10⁻⁴ M
C) 1 × 10⁻⁷ M
D) 1 × 10⁻¹ M
Answer: B
Rationale: pOH = 14 - pH = 4. [OH⁻] = 1 × 10⁻⁴ M.
Question 11
Which of the following is NOT a property of water?
A) High heat capacity
B) Low surface tension
C) High dielectric constant
D) High heat of vaporization
Answer: B
Rationale: Water has high surface tension due to hydrogen bonding, not low.
Question 12
A buffer containing acetic acid (pKa 4.76) and sodium acetate at a 1:1 ratio has a
pH of:
A) 3.76
B) 4.76
C) 5.76
D) 7.00
Answer: B
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VERIFIED QUESTIONS AND ANSWERS WITH RATIONALES -
COMPREHENSIVE LATEST VERSION 2026/2027
(PASS GUARANTEE)
SECTION 1 – WATER, pH, AND BUFFERS (Questions 1–30)
Question 1
Which property of water allows it to act as a universal solvent for polar
substances?
A) High specific heat
B) Cohesion and adhesion
C) Polarity and hydrogen bonding
D) High surface tension
Answer: C
Rationale: Water's polarity and ability to form hydrogen bonds allow it to dissolve
polar and ionic substances. The partial charges interact with solutes.
Question 2
What is the pH of a solution with a hydrogen ion concentration of 1 × 10⁻⁴ M?
A) 2
B) 4
C) 6
D) 8
Answer: B
Rationale: pH = -log[H⁺]. For [H⁺] = 1 × 10⁻⁴, pH = 4.
Question 3
A buffer resists changes in pH by:
A) Absorbing all hydrogen ions
B) Releasing or accepting protons (H⁺)
C) Changing temperature
1
,D) Precipitating out of solution
Answer: B
Rationale: Buffers consist of a weak acid and its conjugate base. They release H⁺
when pH rises and accept H⁺ when pH falls.
Question 4
Which equation is used to calculate the pH of a buffer solution?
A) Michaelis-Menten equation
B) Henderson-Hasselbalch equation
C) Nernst equation
D) Arrhenius equation
Answer: B
Rationale: pH = pKa + log([A⁻]/[HA]) is the Henderson-Hasselbalch equation for
buffer pH.
Question 5
What is the pKa of an acid if the ratio of conjugate base to acid is 10:1 at pH 6?
A) 4
B) 5
C) 6
D) 7
Answer: B
Rationale: pH = pKa + log(10/1) = pKa + 1. If pH = 6, then pKa = 5.
Question 6
The bicarbonate buffer system is important for maintaining:
A) Intracellular pH only
B) Blood pH
C) Stomach acid
D) Urine pH
2
,Answer: B
Rationale: The HCO₃⁻/H₂CO₃ system is the primary blood buffer, maintaining pH
around 7.4.
Question 7
Which of the following is a strong acid?
A) Acetic acid
B) Carbonic acid
C) Hydrochloric acid
D) Phosphoric acid
Answer: C
Rationale: HCl dissociates completely in water, making it a strong acid. The others
are weak acids.
Question 8
The auto-ionization of water produces:
A) H⁺ and OH⁻
B) H₂ and O₂
C) Na⁺ and Cl⁻
D) H₂O₂
Answer: A
Rationale: 2H₂O ⇌ H₃O⁺ + OH⁻ (simplified as H⁺ and OH⁻).
Question 9
A solution with pH 3 is how many times more acidic than a solution with pH 5?
A) 2
B) 10
C) 100
D) 1000
3
, Answer: C
Rationale: Each pH unit represents a 10-fold change. pH 3 vs pH 5 is 10² = 100
times more acidic.
Question 10
What is the [OH⁻] in a solution with pH 10?
A) 1 × 10⁻¹⁰ M
B) 1 × 10⁻⁴ M
C) 1 × 10⁻⁷ M
D) 1 × 10⁻¹ M
Answer: B
Rationale: pOH = 14 - pH = 4. [OH⁻] = 1 × 10⁻⁴ M.
Question 11
Which of the following is NOT a property of water?
A) High heat capacity
B) Low surface tension
C) High dielectric constant
D) High heat of vaporization
Answer: B
Rationale: Water has high surface tension due to hydrogen bonding, not low.
Question 12
A buffer containing acetic acid (pKa 4.76) and sodium acetate at a 1:1 ratio has a
pH of:
A) 3.76
B) 4.76
C) 5.76
D) 7.00
Answer: B
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