Question

You need a 75% alcohol solution. On hand, you have a 25 mL of a 10% alcohol mixture. You also have 80%

alcohol mixture. How much of the 80% mixture will you need to add to obtain the desired solution?
You will need
mL of the 80% solution

Answer 1

325 mL

Explanation:

You will use all 25mL of the 10%, and you will add an amount of 80% solution that will result in a 75% solution.

We need to find the amount of 80% solution added that will produce a 75% alcohol solution.

Let the amount of 80% solution be x.

Amount of alcohol:

10% * 25 mL + 80% * x = 75% * (25 mL + x)

2.5 + 0.8x = 18.75 + 0.75x

0.05x = 16.25

x = 16.25/0.05

x = 325

Answer: 325 mL