Question

How many litres of water must be added to 1 litre of an aqueous solution of HCl with a pH of 1 to create an aqueous solution with a pH of 2?

• A. 0.1 L
• B. 0.9 L
• C. 2.0 L
• D. 9.0L

Answer 1

Answer: (D)

9.0L

Using $pH=-log\left[H^{+}\right]$

Initial pH = 1,

i.e. $\left[H^{+}\right]$ = 0.1 mole/L

New pH = 2,

i.e.$\left[H^{+}\right]$ = 0.01 mole/L

In case of dilution: $M_1{V}_1=M_2{V}_2$

$\therefore$ $0.1\times 1=0.01\times$ $V_2$

$V_2=$ 10 L

Volume of water added,

= V${}_2$ - volume of HCl$=10-1=9L$

The volume of water added = $9L$

Hence, the correct option is $D$.