Pharmaceutical calculations involving percentage solutions MCQs With Answer

Pharmaceutical calculations involving percentage solutions MCQs With Answer

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Pharmaceutical calculations involving percentage solutions are essential for B. Pharm students to master compounding, dispensing, and quality assurance. This concise introduction covers key concepts — percent w/v, v/v, and w/w; conversions to mg/mL, ppm, molarity; dilution and strength calculations; and practical issues for parenteral, topical, and ophthalmic preparations. Accurate percentage calculations ensure correct potency, patient safety, and regulatory compliance. Topics also include assay corrections, density effects on v/v preparations, and interpreting labeled strengths. These MCQs emphasize problem-solving, unit conversions, and real-world compounding scenarios to build competency in pharmaceutical calculations. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What does a 5% w/v solution indicate?

  • 5 g of solute per 100 g of solution
  • 5 mL of solute per 100 mL of solution
  • 5 g of solute per 100 mL of solution
  • 5 g of solute per 1 L of solution

Correct Answer: 5 g of solute per 100 mL of solution

Q2. How many milligrams per milliliter are in a 2% w/v solution?

  • 0.02 mg/mL
  • 20 mg/mL
  • 200 mg/mL
  • 2 mg/mL

Correct Answer: 20 mg/mL

Q3. To prepare 250 mL of a 3% w/v NaCl solution, what mass of NaCl is required?

  • 7.5 g
  • 3.0 g
  • 75 g
  • 0.75 g

Correct Answer: 7.5 g

Q4. A topical cream labeled 1.5% w/w contains how many grams of drug in a 40 g tube?

  • 0.6 g
  • 6.0 g
  • 0.06 g
  • 15 g

Correct Answer: 0.6 g

Q5. Which statement differentiates %v/v from %w/v?

  • %v/v expresses grams of solute in 100 g of solution
  • %v/v expresses volume of solute per 100 mL of solution; %w/v expresses mass of solute per 100 mL of solution
  • %v/v and %w/v are interchangeable for all liquids
  • %w/v expresses volume of solute per 100 mL of solution

Correct Answer: %v/v expresses volume of solute per 100 mL of solution; %w/v expresses mass of solute per 100 mL of solution

Q6. Convert 0.5% w/v to mg/mL.

  • 0.5 mg/mL
  • 5 mg/mL
  • 50 mg/mL
  • 500 mg/mL

Correct Answer: 5 mg/mL

Q7. If a solution is labeled 10% v/v ethanol, what volume of absolute ethanol is required to prepare 500 mL of this solution?

  • 50 mL
  • 10 mL
  • 500 mL
  • 5 mL

Correct Answer: 50 mL

Q8. How many parts per million (ppm) correspond to 0.01% w/v?

  • 1 ppm
  • 10 ppm
  • 100 ppm
  • 1,000 ppm

Correct Answer: 100 ppm

Q9. A labeled drug solution is 20% w/v but assay shows 18% w/v. What is the assay correction factor to adjust calculations?

  • 1.11
  • 0.90
  • 0.18
  • 1.20

Correct Answer: 0.90

Q10. To dilute 5 mL of 10% v/v glycerin to 50 mL final volume, what will be the final %v/v?

  • 1% v/v
  • 10% v/v
  • 0.1% v/v
  • 100% v/v

Correct Answer: 1% v/v

Q11. How many grams of drug are present in 250 mL of 0.02% w/v solution?

  • 0.05 g
  • 0.5 g
  • 5 g
  • 0.005 g

Correct Answer: 0.05 g

Q12. A liquid medication is expressed as 1:200 w/v. What is its percent w/v?

  • 0.5% w/v
  • 2% w/v
  • 0.05% w/v
  • 5% w/v

Correct Answer: 0.5% w/v

Q13. When preparing solutions by weight, why is %w/w preferred for ointments and creams?

  • Because volumes are constant regardless of temperature
  • Because mass-based strength is independent of density and temperature changes
  • Because w/w always gives larger numeric values
  • Because w/w is easier to confuse with v/v

Correct Answer: Because mass-based strength is independent of density and temperature changes

Q14. Convert 15 mg/mL to % w/v.

  • 1.5% w/v
  • 0.015% w/v
  • 15% w/v
  • 0.15% w/v

Correct Answer: 1.5% w/v

Q15. A parenteral solution must be 0.9% w/v NaCl (normal saline). How many grams are needed per liter?

  • 9 g
  • 0.9 g
  • 90 g
  • 900 g

Correct Answer: 9 g

Q16. Which conversion is correct: %w/v to molarity for a drug with MW 250 at 1% w/v?

  • 1% w/v = 0.04 M
  • 1% w/v = 0.4 M
  • 1% w/v = 4 M
  • 1% w/v = 0.004 M

Correct Answer: 1% w/v = 0.04 M

Q17. A 10% w/v antiseptic solution is diluted to 1% w/v. What dilution factor was used?

  • 1:10
  • 10:1
  • 1:100
  • 100:1

Correct Answer: 1:10

Q18. For %w/v preparations, which unit is most commonly used to express concentration in clinical dosing?

  • mg/kg
  • mg/mL
  • g/L only
  • mL/mL

Correct Answer: mg/mL

Q19. If a solution density differs significantly from 1 g/mL, which percentage expression becomes unreliable without correction?

  • %w/w
  • %w/v
  • %v/v
  • ppm

Correct Answer: %v/v

Q20. Calculate volume of solvent needed to prepare 100 mL of 0.2% w/v solution using 0.5 g of drug.

  • 250 mL
  • 2500 mL
  • 40 mL
  • 100 mL (impossible with given mass)

Correct Answer: 40 mL

Q21. A syrup is labeled 20% w/v sucrose. What grams of sucrose are in 500 mL?

  • 100 g
  • 10 g
  • 1,000 g
  • 0.1 g

Correct Answer: 100 g

Q22. A drug has potency 95% by assay. To prepare an intended 1% w/w formulation using the impure drug, what weight of impure drug per 100 g of final product is needed? (Assume no losses.)

  • 1.05 g
  • 0.95 g
  • 1.00 g
  • 10.5 g

Correct Answer: 1.05 g

Q23. Which expresses the correct relationship: percent to ratio strength (w/v)?

  • 1% w/v = 1:1000
  • 1% w/v = 1:100
  • 1% w/v = 1:10
  • 1% w/v = 10:1

Correct Answer: 1% w/v = 1:100

Q24. When converting %w/v to %w/w for an aqueous solution with density 1.05 g/mL, which must be considered?

  • Temperature only
  • Volume change due to solute and density of solution
  • Only molecular weight of solute
  • No correction is needed

Correct Answer: Volume change due to solute and density of solution

Q25. How many milliliters of a 25% v/v alcohol solution are needed to obtain 10 mL of pure alcohol?

  • 40 mL
  • 4 mL
  • 250 mL
  • 2.5 mL

Correct Answer: 40 mL

Q26. A mother tincture is standardized at 1.2% w/v. What mass of active constituent in mg is present in 20 mL? (Assume 1 mL ≈ 1 g)

  • 240 mg
  • 24 mg
  • 2,400 mg
  • 0.24 mg

Correct Answer: 240 mg

Q27. Which conversion is correct: %w/v to ppm for very dilute solutions?

  • 0.0001% = 1 ppm
  • 0.01% = 1 ppm
  • 0.1% = 1 ppm
  • 1% = 1 ppm

Correct Answer: 0.0001% = 1 ppm

Q28. A pharmacist needs to prepare 100 mL of 0.9% w/v solution but only has a 5% w/v stock. What volume of stock is required?

  • 18 mL
  • 45 mL
  • 9 mL
  • 500 mL

Correct Answer: 18 mL

Q29. How is percent strength commonly adjusted when a drug substance has water of crystallization increasing its molecular mass?

  • Ignore water of crystallization; use labeled percent
  • Use assay and molecular mass correction to calculate equivalent active content
  • Always increase percent by 10%
  • Change units from % to ppm only

Correct Answer: Use assay and molecular mass correction to calculate equivalent active content

Q30. For ophthalmic drops, a sodium chloride solution is prescribed as 0.45% w/v. What is the concentration in mg per 5 mL dropper dispensed dose? (Assume one dose = 1 drop = 0.05 mL; calculate per 5 mL total dispensing volume.)

  • 22.5 mg per 5 mL
  • 0.225 mg per 5 mL
  • 225 mg per 5 mL
  • 2.25 mg per 5 mL

Correct Answer: 22.5 mg per 5 mL

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