Question

Molly has 20ml of a 20% sulfuric acid solution and she is mixing it with a 5% sulfuric acid solution. How many millimeters of 5% sulfuric solution must she add in order to end up with a 12% sulfuric acid solution. Round answer to nearest millimeter.

Answer 1

22.86 ml.

Explanation:

Let x ml of 5% sulfuric solution must Molly add to 20ml of 20% solution to get a 12% solution.

Now, x ml of 5% sulfuric acid solution has pure acid of
`(5x)/(100) = 0.05x` ml.

Again, 20 ml of 20% sulfuric acid solution has pure acid of
`(20 * 20)/(100) = 4` ml.

Therefore, we can write the equation as

`(0.05x + 4)/(20 + x) = (12)/(100) =0.12`

⇒ 0.05x + 4 = 2.4 + 0.12x

⇒ 0.07x = 1.6

⇒ x = 22.86 ml. (Answer) (Approximate value)