Question

12. A chemist has 40 mL of a solution that is 50% acid. How much water should he add to make

a solution that is 10% acid?
Total Amount x % Acid = Amount of Acid
Total Amount
% Acid
Amount of Acid
Original Solution
Water
New Solution

Answer 1

Volume of pure Acid in -50- LITRES of the solution= 10- litres. Let “V”- litres of water be added, then

Therefore 10= (50+ V) x8/100 .

So 10= 4 + 8V/100

8V/100 = 10–4= 6

So V= 6 x 100/8= 600/8= 75- LITRES.

So on adding 75- litres of water to the acid solution, the percentage of acid drops to 8% .

Check: Percentage of acid in 125- LITRES of acid solution, which contain 10- LITRES if pure Acid

= 10/125 x 100= 8% .

Explanation: