Question

A student in a chemistry lab has access to two acid solution .The first solution is 20% acid and the second is 45% acid .(the percentage are by volume). How many milliliters of each solution the student mix together to obtain 100 ml of a 30% acid solution?

Answer 1

x = 20% acid = 60 ml

y = 45% acid = 40 ml

Explanation:

Let

x = 20% acid

y = 45% acid

x + y = 100 (1)

.20x + .45y = .3 ×100

.20x + .45y = 30 (2)

From (1)

x + y = 100 (1)

x = 100 - y

Substitute x = 100 - y into (2)

.20x + .45y = 30

.20(100 - y) + .45y = 30

20 - .20y + .45y = 30

- .20y + .45y = 30 - 20

.25y = 10

y = 10/.25

y = 40 ml

Substitute y = 40 into (1)

x + y = 100

x + 40 = 100

x = 100 - 40

x = 60 ml

x = 20% acid = 60 ml

y = 45% acid = 40 ml