66. What is the final percentage strength of a drug if 500 mL of a 20% (v/v) solution is diluted to 1500 mL?
Answer: C
The final percentage strength of the drug is 6.67%.
When 500 mL of a 20% (v/v) solution is diluted to a total volume of 1500 mL, the concentration of the solution decreases. The final percentage strength can be calculated using the formula: (initial concentration × initial volume) / final volume.
A) 1.77%
This option is incorrect as it underestimates the dilution effect. The calculation of the final concentration does not yield this percentage based on the given volumes and initial concentration.
B) 3.23%
This option is also incorrect. While it represents a lower percentage, it does not correctly reflect the dilution of the original solution when applying the appropriate formula to determine the final concentration.
C) 6.67%
This option is correct. By using the formula (20% × 500 mL) / 1500 mL, we find that the final concentration is 6.67%, reflecting the dilution of the original solution to the new total volume.
D) 8.95%
This option is incorrect as it overestimates the concentration after dilution. The calculated value does not correspond to the final strength based on the initial concentration and the total final volume.
Conclusion
The correct answer, 6.67%, accurately represents the final strength of the drug after dilution. All other options fail to match the calculated result based on the initial volume and concentration, confirming that they do not represent the correct outcome of the dilution process.