Question

How much water should be added to $1L$ of an aqueous solution of HCl having $pH=1$ to prepare a solution having $pH=2$?

• A. $0.9L$
• B. $1.0L$
• C. $9.0L$
• D. $10.0L$

Answer 1

Answer: (C)

$9.0L$

At pH = 1

Concentration of $\left[H^{+}\right]={10}^{-1}=0.1M$

At pH=2

Concentration of $\left[H^{+}\right]={10}^{-2}=0.01M$

Now,

$M_1{V}_1=M_2{V}_2$

$0.1\times 1=0.01\times V_2$

$\therefore V_2=10L$

Thus the final volume of the solution is 10L. Hence, 9L should be added to 1L of solution to make pH = 2 from pH = 1.

Hence, the correct option is C.