Question

A laboratory technician needs to make a 135​-liter batch of a 20​% acid solution. How can the laboratory technician combine a batch of an acid solution that is pure acid with another that is 10​% to get the desired​ concentration?

Answer 1

15 liters of pure acid and 120 liters of 10% solution are needed.

Explanation:

Let us assume that,

x = liters of pure acid ,

y = liters of 10​% acid.

As we need a total of 135 liter of batch, so

`x+y=135` ------------------------------1

As we need to make a batch of 20​% acid solution, hence acid content of the mixture of two acids will be same as of the final one, so

`x+0.1y=135* 0.2=27` -----------2

Subtracting equation 2 for 1,

`\Rightarrow x+y-x-0.1y=135-27`

`\Rightarrow y-0.1y=108`

`\Rightarrow 0.9y=108`

`\Rightarrow y=120`

Putting this in the equation 1,

`\Rightarrow x+120=135`

`\Rightarrow x=135-120=15`

Therefore, 15 liters of pure acid and 120 liters of 10% solution are needed.