Final answer:
To calculate the mass of thiopental in 20 mL of an 8% solution, we first determine the volume of the drug using the percentage concentration, and then convert this volume to mass in milligrams, resulting in 1600 mg. The given multiple-choice options seem to contain a typo as none matches the correct amount precisely. The closest option, considering a possible typo, is 160 mg.
Step-by-step explanation:
The student has asked to calculate the amount of drug in milligrams (mg) represented by 20 mL of an 8% thiopental solution. To find this, we use the fact that a percentage concentration is calculated as the volume of solute divided by the volume of solution, multiplied by 100. In this case, an 8% solution means that there are 8 mL of thiopental in every 100 mL of solution. Therefore, to calculate the total amount of thiopental in 20 mL, we can set up the equation:
(8 mL / 100 mL) × 20 mL = X mL of thiopental,
where X is the volume of thiopental present in 20 mL of solution. Doing the math:
(0.08) × 20 mL = 1.6 mL of thiopental.
Next, we need to convert this volume into a mass in milligrams, considering that the density of thiopental is not given, we assume that the solution's density is such that 1 mL equals 1 g (similar to water and for simplicity in calculation). Hence, we simply convert the volume in mL to mass in grams, then to milligrams:
1.6 mL × 1000 mg/g = 1600 mg of thiopental,
which can be then rounded as per significant figures if needed. So the correct answer is 1600 mg, but none of the options A) 1.6 mg B) 8 mg C) 16 mg D) 160 mg matches exactly, it seems there might be a typo. The closest answer by far is D) 160 mg if we misconstrue that the typo was in the conversion from grams to milligrams.