Question

A chemist has a solution that is 20% HIC and a solution that is 50% HCI. How much of each solution should be mixed to attain 300ml of a solution that is 30% HCI?

Answer 1

let the amount of the 20% solution used be x ml
then the amount of the 50% solution used is 300-x m.

solve for x ....
.2x + .5(300-x) = .3(300)
times 10
2x + 5(300-x) = 3(300)

take it from there

Answer 2

It may help to set up a table for these kinds of problems:

............Amount.....%....HCl
Solution 1....x......0.2....0.2x
Solution 2...300-x...0.5....0.5(300-x)
Mixture......300.....0.3....0.3(300)

Equation:
0.2x + 0.5(300-x) = 0.3(300)

Solve for x. (Be sure to list the amount of both solutions!)

I hope this helps.