1
HESI A2 Acid-Base Balance, pH & Buffer
Systems – 200 Practice Questions with
Rationales
Table of Contents
Subtopic 1: Fundamentals of Acid-Base Balance and pH Physiology...............2
Subtopic 2: Respiratory Regulation of Acid-Base Balance..............................10
Subtopic 3: Renal Regulation and Compensation in Acid-Base Imbalance.....18
Subtopic 4: Metabolic Acidosis – Causes, Effects, and Management.............26
Subtopic 5: Metabolic Alkalosis – Causes, Effects, and Management............35
Subtopic 6: Acid-Base Interpretation of ABGs (Arterial Blood Gases)............43
Subtopic 7: Acid-Base Disorders in Clinical Scenarios (Case-Based Questions)
.......................................................................................................................51
Subtopic 8: Buffer Systems in the Human Body (Physiology and Application)
.......................................................................................................................60
Subtopic 9: Respiratory and Renal Compensation Mechanisms.....................68
Subtopic 10: Clinical Management and Nursing Interventions for Acid-Base
Imbalances.....................................................................................................77
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Subtopic 1: Fundamentals of Acid-Base
Balance and pH Physiology
Question 1:
Which of the following best describes the pH of arterial blood in a healthy
adult?
A. 6.8–7.0
B. 7.0–7.25
C. 7.35–7.45
D. 7.50–7.65
Rationale:
Normal arterial blood pH is tightly regulated between 7.35 and 7.45. A value
below 7.35 indicates acidosis, while above 7.45 indicates alkalosis.
Question 2:
What organ system is primarily responsible for regulating pH through
excretion of hydrogen ions and bicarbonate reabsorption?
A. Cardiovascular system
B. Endocrine system
C. Renal system
D. Integumentary system
Rationale:
The kidneys help maintain acid-base balance by excreting hydrogen ions and
reabsorbing bicarbonate, acting slower but more sustained than respiratory
compensation.
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Question 3:
Which buffer system is the most important extracellular buffer in the body?
A. Hemoglobin buffer system
B. Bicarbonate buffer system
C. Phosphate buffer system
D. Protein buffer system
Rationale:
The bicarbonate buffer system is the primary extracellular buffer that
maintains physiological pH by neutralizing excess acids or bases.
Question 4:
A pH of 7.10 in arterial blood indicates:
A. Alkalosis
B. Acidosis
C. Homeostasis
D. Neutrality
Rationale:
A pH of 7.10 is below the normal range, indicating acidosis. Homeostasis
requires a pH between 7.35 and 7.45.
Question 5:
Which of the following components makes up the bicarbonate buffer system?
A. HCl and Cl⁻
B. NaOH and H₂O
C. H₂CO₃ and HCO₃⁻
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D. HPO₄²⁻ and H₂PO₄⁻
Rationale:
The bicarbonate buffer system is composed of carbonic acid (H₂CO₃) and
bicarbonate ion (HCO₃⁻). It balances pH by neutralizing H⁺ or OH⁻ ions.
Question 6:
When hydrogen ion concentration increases, what happens to pH?
A. Increases
B. Decreases
C. Stays the same
D. Becomes alkaline
Rationale:
As hydrogen ion (H⁺) concentration increases, pH decreases, making the
environment more acidic.
Question 7:
Which process results in the formation of carbonic acid in the blood?
A. Excretion by kidneys
B. Digestion in the stomach
C. Reaction of CO₂ with H₂O
D. Protein catabolism
Rationale:
CO₂ combines with water in the blood to form carbonic acid (H₂CO₃), which
plays a key role in acid-base regulation.
HESI A2 Acid-Base Balance, pH & Buffer
Systems – 200 Practice Questions with
Rationales
Table of Contents
Subtopic 1: Fundamentals of Acid-Base Balance and pH Physiology...............2
Subtopic 2: Respiratory Regulation of Acid-Base Balance..............................10
Subtopic 3: Renal Regulation and Compensation in Acid-Base Imbalance.....18
Subtopic 4: Metabolic Acidosis – Causes, Effects, and Management.............26
Subtopic 5: Metabolic Alkalosis – Causes, Effects, and Management............35
Subtopic 6: Acid-Base Interpretation of ABGs (Arterial Blood Gases)............43
Subtopic 7: Acid-Base Disorders in Clinical Scenarios (Case-Based Questions)
.......................................................................................................................51
Subtopic 8: Buffer Systems in the Human Body (Physiology and Application)
.......................................................................................................................60
Subtopic 9: Respiratory and Renal Compensation Mechanisms.....................68
Subtopic 10: Clinical Management and Nursing Interventions for Acid-Base
Imbalances.....................................................................................................77
, 2
Subtopic 1: Fundamentals of Acid-Base
Balance and pH Physiology
Question 1:
Which of the following best describes the pH of arterial blood in a healthy
adult?
A. 6.8–7.0
B. 7.0–7.25
C. 7.35–7.45
D. 7.50–7.65
Rationale:
Normal arterial blood pH is tightly regulated between 7.35 and 7.45. A value
below 7.35 indicates acidosis, while above 7.45 indicates alkalosis.
Question 2:
What organ system is primarily responsible for regulating pH through
excretion of hydrogen ions and bicarbonate reabsorption?
A. Cardiovascular system
B. Endocrine system
C. Renal system
D. Integumentary system
Rationale:
The kidneys help maintain acid-base balance by excreting hydrogen ions and
reabsorbing bicarbonate, acting slower but more sustained than respiratory
compensation.
, 3
Question 3:
Which buffer system is the most important extracellular buffer in the body?
A. Hemoglobin buffer system
B. Bicarbonate buffer system
C. Phosphate buffer system
D. Protein buffer system
Rationale:
The bicarbonate buffer system is the primary extracellular buffer that
maintains physiological pH by neutralizing excess acids or bases.
Question 4:
A pH of 7.10 in arterial blood indicates:
A. Alkalosis
B. Acidosis
C. Homeostasis
D. Neutrality
Rationale:
A pH of 7.10 is below the normal range, indicating acidosis. Homeostasis
requires a pH between 7.35 and 7.45.
Question 5:
Which of the following components makes up the bicarbonate buffer system?
A. HCl and Cl⁻
B. NaOH and H₂O
C. H₂CO₃ and HCO₃⁻
, 4
D. HPO₄²⁻ and H₂PO₄⁻
Rationale:
The bicarbonate buffer system is composed of carbonic acid (H₂CO₃) and
bicarbonate ion (HCO₃⁻). It balances pH by neutralizing H⁺ or OH⁻ ions.
Question 6:
When hydrogen ion concentration increases, what happens to pH?
A. Increases
B. Decreases
C. Stays the same
D. Becomes alkaline
Rationale:
As hydrogen ion (H⁺) concentration increases, pH decreases, making the
environment more acidic.
Question 7:
Which process results in the formation of carbonic acid in the blood?
A. Excretion by kidneys
B. Digestion in the stomach
C. Reaction of CO₂ with H₂O
D. Protein catabolism
Rationale:
CO₂ combines with water in the blood to form carbonic acid (H₂CO₃), which
plays a key role in acid-base regulation.
