Proof spirit calculations and alcohol strength adjustments MCQs With Answer is a focused review for B.Pharm students covering ABV, proof systems, dilution mathematics and compounding practice. This introduction highlights key concepts: proof (US and historical UK definitions), percent v/v versus w/w, use of C1V1=C2V2 for dilution, specific gravity of ethanol, temperature effects on hydrometer readings, and practical alcohol-strength adjustments in pharmaceutical formulations (elixirs, tinctures, preservatives). Questions emphasize calculations, measurement accuracy, regulatory USP grades, and stability implications to prepare you for real-world compounding and exam scenarios. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. According to the US system, what is the proof of a spirit labeled 40% v/v?
- 40 proof
- 80 proof
- 100 proof
- 20 proof
Correct Answer: 80 proof
Q2. What is the ABV of a spirit labeled 120 proof (US)?
- 60% v/v
- 120% v/v
- 30% v/v
- 100% v/v
Correct Answer: 60% v/v
Q3. To prepare 1 L of 10% v/v alcohol from an 80% v/v stock, what volume of stock is required (approx)?
- 100 mL
- 125 mL
- 250 mL
- 800 mL
Correct Answer: 125 mL
Q4. How many mL of 95% v/v ethanol are needed to make 500 mL of 60% v/v solution (rounded)?
- 300 mL
- 316 mL
- 250 mL
- 400 mL
Correct Answer: 316 mL
Q5. If you mix 200 mL of 40% ABV with 300 mL of 20% ABV, what is the final ABV (assuming additive volumes)?
- 24% v/v
- 28% v/v
- 30% v/v
- 32% v/v
Correct Answer: 28% v/v
Q6. You have 750 mL of 70% v/v spirit and want to dilute it to 50% v/v. How much water must you add (mL)?
- 150 mL
- 300 mL
- 525 mL
- 375 mL
Correct Answer: 300 mL
Q7. What is the approximate density (specific gravity) of pure ethanol at 20°C?
- 0.789 g/mL
- 1.000 g/mL
- 0.950 g/mL
- 0.650 g/mL
Correct Answer: 0.789 g/mL
Q8. Which formula is most appropriate for routine alcohol dilution calculations in pharmacy compounding?
- C1 + V1 = C2 + V2
- C1V1 = C2V2
- C1/V1 = C2/V2
- C1 – V1 = C2 – V2
Correct Answer: C1V1 = C2V2
Q9. Which concentration expression denotes volume of solute per total volume of solution?
- % w/w
- % v/v
- % w/v
- Molarity
Correct Answer: % v/v
Q10. When using a hydrometer to measure alcohol strength, why is temperature important?
- Temperature does not affect hydrometer readings
- Hydrometer readings depend on calibration temperature and require correction for accurate ABV
- Hydrometers measure only proof, not ABV
- Temperature only affects color, not density
Correct Answer: Hydrometer readings depend on calibration temperature and require correction for accurate ABV
Q11. Which designation is the appropriate USP grade for ethyl alcohol used in pharmaceutical compounding?
- Isopropyl alcohol, USP
- Ethyl alcohol, USP
- Denatured alcohol, food grade
- Rubbing alcohol
Correct Answer: Ethyl alcohol, USP
Q12. If 1 L of 95% v/v ethanol is mixed with 1 L of water (assume additive volumes), what is the approximate ABV of the mixture?
- 95% v/v
- 47.5% v/v
- 50% v/v
- 25% v/v
Correct Answer: 47.5% v/v
Q13. How many mL of pure ethanol are present in 250 mL of a 40% v/v solution?
- 40 mL
- 100 mL
- 60 mL
- 150 mL
Correct Answer: 100 mL
Q14. When adjusting alcohol strength in elixirs, what must the pharmacist primarily consider?
- Only color changes
- Solubility of active ingredients and preservative efficacy of alcohol
- Flavor exclusively
- Cost of water
Correct Answer: Solubility of active ingredients and preservative efficacy of alcohol
Q15. To prepare 1 L of 30% v/v solution from a 95% v/v stock, approximately how much stock is required?
- 250 mL
- 316 mL
- 500 mL
- 400 mL
Correct Answer: 316 mL
Q16. In the US proof system, what does the term “100 proof spirit” correspond to in ABV?
- 100% v/v
- 57.15% v/v
- 50% v/v
- 10% v/v
Correct Answer: 50% v/v
Q17. Historically in the British (Sikes) proof system, a spirit of 100° proof corresponds approximately to which ABV?
- 50% v/v
- 57.15% v/v
- 40% v/v
- 100% v/v
Correct Answer: 57.15% v/v
Q18. Mixing equal volumes (250 mL + 250 mL) of 60% and 40% ABV yields what final ABV?
- 45% v/v
- 50% v/v
- 40% v/v
- 60% v/v
Correct Answer: 50% v/v
Q19. If a partially filled container of spirit is left open and solvent (water) preferentially evaporates less than ethanol, what happens to the alcohol concentration?
- Alcohol concentration decreases
- Alcohol concentration remains constant
- Alcohol concentration increases
- Volume increases without concentration change
Correct Answer: Alcohol concentration increases
Q20. A bottle labeled 80 proof is equivalent to what ethanol volume in 500 mL of that spirit?
- 200 mL ethanol
- 400 mL ethanol
- 80 mL ethanol
- 100 mL ethanol
Correct Answer: 200 mL ethanol
Q21. For accurate volumetric alcohol measurements during compounding, which practice is recommended?
- Use any container at room temperature
- Use calibrated volumetric glassware and account for temperature
- Estimate by eye using syringes
- Measure mass only and ignore volume
Correct Answer: Use calibrated volumetric glassware and account for temperature
Q22. To prepare 250 mL of 15% v/v from 70% v/v ethanol, approximately how much 70% stock is needed?
- 25 mL
- 54 mL
- 150 mL
- 75 mL
Correct Answer: 54 mL
Q23. Which concentration type expresses mass of solute per total mass of solution?
- % v/v
- % w/w
- % w/v
- Molarity
Correct Answer: % w/w
Q24. How should a hydrometer reading be corrected if the sample temperature differs from the hydrometer calibration temperature?
- No correction is needed
- Apply temperature correction factors from standard tables
- Subtract 5% from the reading
- Multiply reading by sample temperature (°C)
Correct Answer: Apply temperature correction factors from standard tables
Q25. When a concentration is given as % w/v, what does it mean?
- g of solute per 100 mL of solution
- mL of solute per 100 mL of solution
- g of solute per 100 g of solution
- mol of solute per litre
Correct Answer: g of solute per 100 mL of solution
Q26. Adding alcohol to water typically does what to the mixture’s density compared to pure water?
- Increases density above 1.0 g/mL
- Decreases density below 1.0 g/mL
- Leaves density exactly 1.0 g/mL
- Makes density infinite
Correct Answer: Decreases density below 1.0 g/mL
Q27. What is the ABV of a mixture made by adding 100 mL of 95% ethanol to 400 mL of water (assume additive volumes)?
- 19% v/v
- 95% v/v
- 24% v/v
- 5% v/v
Correct Answer: 19% v/v
Q28. To prepare 200 mL of 40% v/v solution from a 90% v/v stock, approximately how much stock is needed?
- 44 mL
- 89 mL
- 100 mL
- 80 mL
Correct Answer: 89 mL
Q29. How much water must be added to 500 mL of 40% v/v spirit to reduce it to 20% v/v (assume additive volumes)?
- 250 mL
- 400 mL
- 500 mL
- 0 mL
Correct Answer: 500 mL
Q30. Why are accurate alcohol-strength adjustments critical in pharmaceutical formulations?
- They only affect taste but not drug performance
- They ensure solubility, stability, dosing accuracy, and preservative efficacy
- They are unimportant; any approximation is acceptable
- They only affect packaging color
Correct Answer: They ensure solubility, stability, dosing accuracy, and preservative efficacy
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