Question

Roman mixes 12 litres of 8% acid solution with a 20% acid solution, which results in a 16% acid solution. How do you find the number of litres of 20% acid solution in the new mixture?

Answer 1

The volume of 20 % acid is 24 L.

Explanation:

We can use the "volume × concentration" formula to work out the answer.

`"Volume of 8 % acid + volume of 20 % acid = volume of 16 % acid"`

Let `x` be the volume of 20 % acid.

Then `(12 + x)color(white)(l) "L"` is the new volume of the 16 % acid.

We can write

`V_1c_1 + V_2c_2 = V_3c_3`

`12 color(red)(cancel(color(black)("L"))) × 8 color(red)(cancel(color(black)(%))) + x color(red)(cancel(color(black)("L"))) × 20 color(red)(cancel(color(black)(%))) = (12 +x) color(red)(cancel(color(black)("L"))) × 16 color(red)(cancel(color(black)(%)))`

`96 + 20x = 192 + 16x`

`4x = "192 - 96" = 96`

`x = 96/4 = 24`

∴ The volume of 20 % acid is 24 L.