Problema Solution

You need a 40% alcohol solution. On hand, you have a 600 mL of a 85% alcohol mixture. How much pure water will you need to add to obtain the desired solution? mL of pure water

to obtain mL of the desired 40% solution.

Answer provided by our tutors

For simplicity.  We have 600 mL of 85% alcohol mixture = 510 mL of alcohol.  510 / 40% = amount of total liquid we need to have = 1,274.  We already have 600 mL of liquid so 1,274 mL - 600 mL = 674 mL of pure water needed to get the desired solution.