Fluids, Electrolytes and Acid-Base MC Questions & Answer 2025 | 100% Correct
1. What is the normal arterial pH range?
A. 7.00–7.20 → Incorrect. This range indicates severe acidemia.
B. 7.25–7.35 → Incorrect. This is slightly acidic and below the normal range.
C. 7.35–7.45 → Correct. This is the normal physiological pH range for arterial blood.
D. 7.45–7.55 → Incorrect. This range is slightly alkaline and may suggest alkalosis.
2. What is the normal plasma concentration of bicarbonate?
A. 18 mM → Incorrect. This is lower than normal and seen in metabolic acidosis.
B. 24 mM → Correct. The normal HCO concentration is about 24 mM.
C. 28 mM → Incorrect. This value is elevated and may be seen in metabolic alkalosis.
D. 32 mM → Incorrect. This is abnormally high and usually pathological.
3. According to the Henderson-Hasselbalch principle, pH depends on the ratio of:
A. HCO to H → Incorrect. H is not part of the ratio; it's a result.
B. HCO to carbonic acid → Correct. The equation compares base to acid (HCO /H CO or CO ).
C. CO to O → Incorrect. Oxygen is unrelated to the buffering system here.
D. Na to Cl → Incorrect. These ions are used in anion gap calculations, not in pH buffering.
4. What is the main renal compensation for acidosis?
A. Decrease bicarbonate excretion → Incorrect. This may help slightly, but more active mechanisms are
used.
B. Increase hydrogen excretion and generate new HCO → Correct. The kidneys secrete H and
produce new bicarbonate to restore pH.
C. Increase CO retention → Incorrect. That’s a respiratory response, not renal.
D. Increase chloride excretion → Incorrect. Chloride excretion does not directly affect acid-base
compensation.
5. What ratio of bicarbonate to carbonic acid corresponds to a pH of 7.40?
A. 10:1 → Incorrect. This ratio would give a lower pH than normal.
B. 15:1 → Incorrect. Still too low to achieve normal pH.
C. 20:1 → Correct. The ideal ratio for a pH of 7.40 is approximately 20:1 HCO to H CO .
D. 25:1 → Incorrect. This would result in a more alkaline pH.
6. Which organ responds immediately to a drop in pH?
A. Liver → Incorrect. The liver processes ammonia and urea, but does not regulate pH rapidly.
B. Kidneys → Incorrect. Renal compensation takes hours to days.
C. Pancreas → Incorrect. The pancreas secretes bicarbonate but does not regulate systemic pH rapidly.
D. Lungs → Correct. Respiratory rate adjusts within minutes to expel CO and compensate for acidosis.
7. Which of the following is NOT a cause of metabolic acidosis?
A. Severe diarrhea → Incorrect. Diarrhea causes loss of bicarbonate, leading to acidosis.
B. Chronic renal failure → Incorrect. Impaired acid excretion leads to metabolic acidosis.
, C. Hyperventilation → Correct. This causes respiratory alkalosis, not metabolic
acidosis.
D. Diabetic ketoacidosis → Incorrect. This is a classic cause of metabolic acidosis.
8. What is the most important diagnostic value for
identifying an anion gap? A. Total calcium → Incorrect.
Calcium is not involved in calculating anion gap.
B. Serum osmolarity → Incorrect. Osmolarity reflects solute concentration,
not acid-base balance.
C. Serum sodium → Incorrect. Sodium alone is insufficient without
considering other ions.
D. (Na⁺ + K⁺) – (Cl⁻ + HCO₃⁻) → Correct. This formula gives the anion gap,
useful for categorizing metabolic acidosis.
9. Which of the following results in a normal anion gap
metabolic acidosis? A. Methanol poisoning → Incorrect. This
causes a high anion gap.
B. Lactic acidosis → Incorrect. Lactate accumulation increases the anion gap.
C. Diarrhea → Correct. Bicarbonate loss in stool leads to acidosis with normal
anion gap.
D. Diabetic ketoacidosis → Incorrect. Ketones increase the anion gap.
10. What is the most serious neurological complication of
metabolic acidosis? A. Insomnia → Incorrect. This is not a
serious acute complication.
B. Mania → Incorrect. Mania is psychiatric, not a direct result of acidosis.
C. Coma → Correct. Severe acidosis can depress CNS function, leading to coma.
D. Muscle rigidity → Incorrect. More characteristic of electrolyte disturbances
like calcium imbalance.
11. What is the expected compensatory mechanism for
metabolic acidosis?
A. Increased respiratory rate → Incorrect. While respiratory compensation
helps, this is not the primary
compensatory mechanism.
B. Decreased renal H⁺ excretion → Incorrect. This would worsen acidosis.
C. Increased renal H⁺ excretion and HCO₃⁻ reabsorption → Correct. The
kidneys excrete more acid and reabsorb bicarbonate to buffer.
1. What is the normal arterial pH range?
A. 7.00–7.20 → Incorrect. This range indicates severe acidemia.
B. 7.25–7.35 → Incorrect. This is slightly acidic and below the normal range.
C. 7.35–7.45 → Correct. This is the normal physiological pH range for arterial blood.
D. 7.45–7.55 → Incorrect. This range is slightly alkaline and may suggest alkalosis.
2. What is the normal plasma concentration of bicarbonate?
A. 18 mM → Incorrect. This is lower than normal and seen in metabolic acidosis.
B. 24 mM → Correct. The normal HCO concentration is about 24 mM.
C. 28 mM → Incorrect. This value is elevated and may be seen in metabolic alkalosis.
D. 32 mM → Incorrect. This is abnormally high and usually pathological.
3. According to the Henderson-Hasselbalch principle, pH depends on the ratio of:
A. HCO to H → Incorrect. H is not part of the ratio; it's a result.
B. HCO to carbonic acid → Correct. The equation compares base to acid (HCO /H CO or CO ).
C. CO to O → Incorrect. Oxygen is unrelated to the buffering system here.
D. Na to Cl → Incorrect. These ions are used in anion gap calculations, not in pH buffering.
4. What is the main renal compensation for acidosis?
A. Decrease bicarbonate excretion → Incorrect. This may help slightly, but more active mechanisms are
used.
B. Increase hydrogen excretion and generate new HCO → Correct. The kidneys secrete H and
produce new bicarbonate to restore pH.
C. Increase CO retention → Incorrect. That’s a respiratory response, not renal.
D. Increase chloride excretion → Incorrect. Chloride excretion does not directly affect acid-base
compensation.
5. What ratio of bicarbonate to carbonic acid corresponds to a pH of 7.40?
A. 10:1 → Incorrect. This ratio would give a lower pH than normal.
B. 15:1 → Incorrect. Still too low to achieve normal pH.
C. 20:1 → Correct. The ideal ratio for a pH of 7.40 is approximately 20:1 HCO to H CO .
D. 25:1 → Incorrect. This would result in a more alkaline pH.
6. Which organ responds immediately to a drop in pH?
A. Liver → Incorrect. The liver processes ammonia and urea, but does not regulate pH rapidly.
B. Kidneys → Incorrect. Renal compensation takes hours to days.
C. Pancreas → Incorrect. The pancreas secretes bicarbonate but does not regulate systemic pH rapidly.
D. Lungs → Correct. Respiratory rate adjusts within minutes to expel CO and compensate for acidosis.
7. Which of the following is NOT a cause of metabolic acidosis?
A. Severe diarrhea → Incorrect. Diarrhea causes loss of bicarbonate, leading to acidosis.
B. Chronic renal failure → Incorrect. Impaired acid excretion leads to metabolic acidosis.
, C. Hyperventilation → Correct. This causes respiratory alkalosis, not metabolic
acidosis.
D. Diabetic ketoacidosis → Incorrect. This is a classic cause of metabolic acidosis.
8. What is the most important diagnostic value for
identifying an anion gap? A. Total calcium → Incorrect.
Calcium is not involved in calculating anion gap.
B. Serum osmolarity → Incorrect. Osmolarity reflects solute concentration,
not acid-base balance.
C. Serum sodium → Incorrect. Sodium alone is insufficient without
considering other ions.
D. (Na⁺ + K⁺) – (Cl⁻ + HCO₃⁻) → Correct. This formula gives the anion gap,
useful for categorizing metabolic acidosis.
9. Which of the following results in a normal anion gap
metabolic acidosis? A. Methanol poisoning → Incorrect. This
causes a high anion gap.
B. Lactic acidosis → Incorrect. Lactate accumulation increases the anion gap.
C. Diarrhea → Correct. Bicarbonate loss in stool leads to acidosis with normal
anion gap.
D. Diabetic ketoacidosis → Incorrect. Ketones increase the anion gap.
10. What is the most serious neurological complication of
metabolic acidosis? A. Insomnia → Incorrect. This is not a
serious acute complication.
B. Mania → Incorrect. Mania is psychiatric, not a direct result of acidosis.
C. Coma → Correct. Severe acidosis can depress CNS function, leading to coma.
D. Muscle rigidity → Incorrect. More characteristic of electrolyte disturbances
like calcium imbalance.
11. What is the expected compensatory mechanism for
metabolic acidosis?
A. Increased respiratory rate → Incorrect. While respiratory compensation
helps, this is not the primary
compensatory mechanism.
B. Decreased renal H⁺ excretion → Incorrect. This would worsen acidosis.
C. Increased renal H⁺ excretion and HCO₃⁻ reabsorption → Correct. The
kidneys excrete more acid and reabsorb bicarbonate to buffer.
