, Question 1
A solution contains 0.25 mol of KCl dissolved in enough water to make 500
mL. If the solution is diluted to 2.0 L, what is the final osmolarity (mOsm/L)
assuming complete dissociation?
A. 125 mOsm/L
B. 250 mOsm/L
C. 500 mOsm/L
D. 1000 mOsm/L
Correct Answer: B - 250 mOsm/L
RATIONALE
Initial molarity = 0.25 mol / 0.5 L = 0.5 M; after dilution to 2.0 L,
molarity = 0.25 mol / 2.0 L = 0.125 M. KCl dissociates into 2 ions, so
osmolarity = 0.125 M × 2 = 0.25 Osm/L = 250 mOsm/L. Distractors
reflect failure to account for dilution, dissociation, or both.
Question 2
During a study on skeletal muscle, a toxin prevents acetylcholine from binding
to its receptors. Which direct consequence is most consistent with this
mechanism?
A. Prolonged depolarization of the motor end plate
B. Failure of synaptic vesicles to fuse with the presynaptic membrane
C. Inability to generate an end-plate potential and muscle contraction
D. Increased calcium release from the sarcoplasmic reticulum
Correct Answer: C - Inability to generate an end-plate potential
and muscle contraction
Page 2
, RATIONALE
Acetylcholine binding to nicotinic receptors on the motor end plate is
required to generate an end-plate potential and subsequent muscle
contraction. Blocking this binding prevents depolarization and
contraction, not vesicle fusion or calcium release. Distractors
misattribute steps in excitation-contraction coupling.
Question 3
A researcher finds that individuals with a specific allele have a 3-fold increased
risk of a disease, but the allele is present in 40% of the population. Which
statement best interprets this finding?
A. The allele is likely the sole cause of the disease.
B. The allele has low attributable risk because it is common.
C. The allele has high positive predictive value for the disease.
D. The allele's population attributable risk is likely substantial despite
modest relative risk.
Correct Answer: D - The allele's population attributable risk is
likely substantial despite modest relative risk.
RATIONALE
A common allele with a modest relative risk can still contribute
substantially to disease burden at the population level, as reflected in
population attributable risk. The other options overstate causality,
confuse predictive value with risk, or misapply attributable risk
concepts.
Question 4
A gas occupies 2.0 L at 27°C and 1.0 atm. If the temperature is raised to 327°C
while pressure is held constant, what is the new volume?
A. 1.0 L
B. 2.0 L
C. 4.0 L
Page 3
, D. 8.0 L
Correct Answer: C - 4.0 L
RATIONALE
Using Charles's law (V1/T1 = V2/T2) with Kelvin: T1 = 300 K, T2 =
600 K, so V2 = 2.0 L × (600/300) = 4.0 L. Distractors arise from using
Celsius, inverting the ratio, or misapplying the gas law.
Question 5
A patient with severe diarrhea loses significant bicarbonate-rich fluid. Which
acid-base disturbance is most likely, and what is the expected respiratory
response?
A. Metabolic alkalosis; hypoventilation
B. Metabolic acidosis; hyperventilation
C. Respiratory acidosis; hypoventilation
D. Respiratory alkalosis; hyperventilation
Correct Answer: B - Metabolic acidosis; hyperventilation
RATIONALE
Loss of bicarbonate causes metabolic acidosis, which stimulates
chemoreceptors to increase ventilation (hyperventilation) to blow off
CO2 and compensate. The other options misidentify the primary
disturbance or the compensatory response.
Question 6
A nurse must administer 0.5 g of a drug. The available vial contains 250
mg/mL. How many mL should be drawn up?
A. 0.5 mL
B. 1 mL
C. 2 mL
D. 5 mL
Page 4
A solution contains 0.25 mol of KCl dissolved in enough water to make 500
mL. If the solution is diluted to 2.0 L, what is the final osmolarity (mOsm/L)
assuming complete dissociation?
A. 125 mOsm/L
B. 250 mOsm/L
C. 500 mOsm/L
D. 1000 mOsm/L
Correct Answer: B - 250 mOsm/L
RATIONALE
Initial molarity = 0.25 mol / 0.5 L = 0.5 M; after dilution to 2.0 L,
molarity = 0.25 mol / 2.0 L = 0.125 M. KCl dissociates into 2 ions, so
osmolarity = 0.125 M × 2 = 0.25 Osm/L = 250 mOsm/L. Distractors
reflect failure to account for dilution, dissociation, or both.
Question 2
During a study on skeletal muscle, a toxin prevents acetylcholine from binding
to its receptors. Which direct consequence is most consistent with this
mechanism?
A. Prolonged depolarization of the motor end plate
B. Failure of synaptic vesicles to fuse with the presynaptic membrane
C. Inability to generate an end-plate potential and muscle contraction
D. Increased calcium release from the sarcoplasmic reticulum
Correct Answer: C - Inability to generate an end-plate potential
and muscle contraction
Page 2
, RATIONALE
Acetylcholine binding to nicotinic receptors on the motor end plate is
required to generate an end-plate potential and subsequent muscle
contraction. Blocking this binding prevents depolarization and
contraction, not vesicle fusion or calcium release. Distractors
misattribute steps in excitation-contraction coupling.
Question 3
A researcher finds that individuals with a specific allele have a 3-fold increased
risk of a disease, but the allele is present in 40% of the population. Which
statement best interprets this finding?
A. The allele is likely the sole cause of the disease.
B. The allele has low attributable risk because it is common.
C. The allele has high positive predictive value for the disease.
D. The allele's population attributable risk is likely substantial despite
modest relative risk.
Correct Answer: D - The allele's population attributable risk is
likely substantial despite modest relative risk.
RATIONALE
A common allele with a modest relative risk can still contribute
substantially to disease burden at the population level, as reflected in
population attributable risk. The other options overstate causality,
confuse predictive value with risk, or misapply attributable risk
concepts.
Question 4
A gas occupies 2.0 L at 27°C and 1.0 atm. If the temperature is raised to 327°C
while pressure is held constant, what is the new volume?
A. 1.0 L
B. 2.0 L
C. 4.0 L
Page 3
, D. 8.0 L
Correct Answer: C - 4.0 L
RATIONALE
Using Charles's law (V1/T1 = V2/T2) with Kelvin: T1 = 300 K, T2 =
600 K, so V2 = 2.0 L × (600/300) = 4.0 L. Distractors arise from using
Celsius, inverting the ratio, or misapplying the gas law.
Question 5
A patient with severe diarrhea loses significant bicarbonate-rich fluid. Which
acid-base disturbance is most likely, and what is the expected respiratory
response?
A. Metabolic alkalosis; hypoventilation
B. Metabolic acidosis; hyperventilation
C. Respiratory acidosis; hypoventilation
D. Respiratory alkalosis; hyperventilation
Correct Answer: B - Metabolic acidosis; hyperventilation
RATIONALE
Loss of bicarbonate causes metabolic acidosis, which stimulates
chemoreceptors to increase ventilation (hyperventilation) to blow off
CO2 and compensate. The other options misidentify the primary
disturbance or the compensatory response.
Question 6
A nurse must administer 0.5 g of a drug. The available vial contains 250
mg/mL. How many mL should be drawn up?
A. 0.5 mL
B. 1 mL
C. 2 mL
D. 5 mL
Page 4
