Final answer:
To prepare a solution with a 1:8 concentration of drug in 400mL of sterile water, you would need 50 mL of the drug.
Step-by-step explanation:
To prepare a solution with a 1:8 concentration of drug in 400mL of sterile water, you need to calculate the amount of drug required. The concentration of the drug is defined as the ratio of the amount of drug to the total volume of the solution. In this case, the concentration is 1:8, which means that for every part of drug, there are 8 parts of total solution. Therefore, to find the amount of drug needed, you can set up a proportion:
1 part drug : 8 parts total solution = x g drug : 400 mL total solution
Simplifying the proportion gives you:
x = (1/8) * 400 mL = 50 mL
So, you would need 50 mL of drug to prepare 400mL of the solution.