Question

You need a 70% alcohol solution. On hand, you have a 840 mL of a 95% 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 70% solution.

Answer 1

Step-by-step explanation:

If x is the volume of pure water:

Initial + added = final

0.95 (840) + 0 (x) = 0.70 (840 + x)

798 = 588 + 0.70 x

x = 300

840 + x = 1140

You need to add 300 mL of pure water to obtain 1140 mL of the desired 70% solution.