Massachusetts Pharmacy Technician License Practice Test

If 120 mL of a 20% povidone iodine solution is diluted with 0.9% sodium chloride, what is the final concentration of povidone iodine?

1. 10%

2. 5%

3. 15%

4. 2%

The correct answer is: 5%

To determine the final concentration of povidone iodine after diluting the original solution, we first need to understand how dilution affects concentration. The original volume of the povidone iodine solution is 120 mL and it has a concentration of 20%. This means that in the 120 mL solution, there are 24 mL of pure povidone iodine (since 20% of 120 mL equals 24 mL). When diluting this solution with 0.9% sodium chloride, the total volume of the resulting solution will increase. The concentration of a solution is defined as the amount of solute divided by the total volume of the solution. When you add a volume of sodium chloride solution, you are increasing the total volume without adding any additional povidone iodine, which decreases the overall concentration of povidone iodine in the new mixture. To find the final concentration, the total amount of povidone iodine (24 mL) is divided by the new total volume (the original 120 mL plus the volume of sodium chloride solution added). To find the correct choice based on plausible dilution scenarios: - If you calculate for a significant amount of sodium chloride solution added, the resulting concentration could have been