Question

A Chemist has 100g of 25% acid solution. How much of this solution does he need to drain and replace with a 70% acid solution to obtain 100g of 60% acid solution?

Answer 1

Hint: 25 % of acid means 25 gm of acid in 75 gm of the water. The addition of more water to the concentrated solution of chemicals is called dilution. By diluting the acids the concentration of the acid is going to decrease.

Complete step-by-step answer:- In the question it is given that a chemist has 100 g of 25% acid solution and he wants to drain it and add 7 % of acid to get 100 g of 60% of the acid.
- We have to calculate how much of 100 g of 25 % is supposed to be discarded to get 100 g of 60 % acid solution.
- Assume that x = mass of the 100 g of 25% acid
- Then automatically x = the mass of the 70 % acid
- So 100 – x will be the mass of the 25 % acid remaining.
- Therefore we can write the above data in the following way
Mass of the acid in 25 % solution + Mass of the acid 70 % solution = Mass of the acid in 60% solution
0.25 (100-x) + 0.7 x = (0.60) (100)
0.45 x = 35
x = 78 grams.
- Means the chemist has to drain 78 grams of the 25 % of the acid to get 100 g of 60% acid solution.

Note: We are supposed to add acid to the water not water to the acid. At the time of dilution we are supposed to add acid to the water to avoid the chemical accidents. A mixture of solute and solvent is called solution.