40. If 500 mg of a drug is used to prepare 80 mL of a syrup, how much of the drug in mg is contained in each teaspoonful dose?
Answer: C
Each teaspoonful dose contains 31.25 mg of the drug.
To determine the amount of drug in each teaspoonful dose, we first calculate the concentration of the drug in the syrup. Since 500 mg of drug is dissolved in 80 mL, we find the amount per mL and then calculate the amount in a typical teaspoonful, which is approximately 5 mL.
A) 6.25
This option is incorrect as it suggests that each teaspoonful contains only 6.25 mg of the drug. Since each teaspoonful holds approximately 5 mL, the calculation should show a higher concentration based on the total volume of the syrup.
B) 18.75
This option is also incorrect. It implies that each teaspoonful contains 18.75 mg of the drug, which does not align with the calculated concentration from the total 500 mg in 80 mL. The actual concentration is higher than this value.
C) 31.25
This is the correct answer. To find the amount of drug in each teaspoonful, we first calculate the concentration: 500 mg / 80 mL = 6.25 mg/mL. For a 5 mL dose, we multiply 6.25 mg/mL by 5 mL, resulting in 31.25 mg per teaspoonful.
D) 93.75
This option is incorrect as it implies that each teaspoonful contains 93.75 mg of the drug, which exceeds the total concentration available in the syrup. The total amount of drug is limited to 500 mg distributed across 80 mL, making this figure unattainable for a single teaspoonful.
Conclusion
The correct answer of 31.25 mg per teaspoonful is derived from accurate calculations based on the concentration of the drug in the syrup. All other options fail because they either underestimate or overestimate the drug concentration that can be derived from the given total volume and mass of the drug dissolved.