Question

pH of 1 litre of HCL solution is 1. How much water (in litres) is added to make pH=2?

Answer 1

The correct answer is 9.
pH=1 ∴ [H+]=10−1=0.1 M
pH=2 ∴ [H+]=10−2=0.01 M
For dilution of HCl, M1V1=M2V2
0.1×1=0.01×V2
V2=10 L
Volume of water to be added = 10 - 1 = 9 L