Question

A chemist is mixing a 30% salt solution with a 20% salt solution to make 35 L of a new solution that will contain 25% salt. How much of the 30% solution should the chemist use?

Answer 1

17.5 L

Explanation:

x L of 30% solution , has 0.30x salt

35 L of 25 % solution, has (0.25*35) salt

(35 - x)L 20% solution, has 0.20*(35 - x) salt

Mass of salt before mixing = mass of salt after mixing

0.3x + 0.2(35 - x) = 0.25* 35

0.3 x + 7 - 0.2x = 8.75

0.1x = 8.75 -7

0.1x = 1.75

x = 17.5 L