Question

How many litres of water must be added to 2 litre aqueous solution of HCl with a pH of 1 to create an aqueous solution with pH of 2 ?
1. 10 L
2. 0.9 L
3. 2 L
4. 18 L

Answer 1

Correct Answer - Option 4 : 18 L

pH = 1  ⇒         [H+] = 10^–1 = 0.1 M

pH = 2 ⇒          [H+] = 10^–2 = 0.01 M

for dilution of HCl  M₁V₁ = M₂V₂ 

0.1 × 2 = 0.01 × V₂ 

V₂ = 20 L

Volume of water added = 20 – 2 = 18 litre