Question

George wishes to increase the percent of acid in 50 ml of a 15% acid solution in water

to 25% acid. How much pure acid should he add?

Answer 1

screw this question

Explanation:

To change from 15% to 25% he needs to add 10%.

If the solution is 50ml then he needs to add 10% which is 5ml... But if he adds 5 ml then the solution will be 55ml total, so that doesn't make sense. He has to take some of the solution that's not acid before adding the 5ml...

Answer 2

20/3 ml

Explanation:

Original solution volume is 50ml out of which 15% is acid

Vol of acid in solution = 15% x 50 = 7.5 ml

Let's add X ml of acid to solution so that acid % is 25%

New acid volume = X + 7.5

New solution volume = X + 50

Using ratio of acid/solution gives us (X+7.5)/(X+50) = 25/100

or,

(X + 7.5)/(X+50) = 1/4

Cross-multiplying

4(X+7.5) = X + 50

4X + 30 = X + 50

3X = 20

X = 20/3 ANS