Question

If water is added to a volumetric flask containing $1$ ml of $0.1MHCl$ till the volume of the solution becomes 1 L, then the pH of the solution becomes:

• A. $4$
• B. $8$
• C. $3$
• D. $6$

Answer 1

The correct option is A $4$

The expression for normality is given below:

$V_1{N}_1=V_2{N}_2$

We have $V_1=1$ ml, $N_1=0.1N$ (since basicity is 1) and $V_2=1$ L $=1000$ ml

Substituting values in the above expression, we get

$1\times 0.1=1000\times N_2$

Hence, the normality of the resulting solution is ${10}^{-4}$ N.

This is equal to the hydrogen ion concentration as $HCl$ being a strong electrolyte completely dissociates in the solution.

Hence, the pH of the solution is as given below:

$pH=-log\left[H^{+}\right]=-log\left({10}^{-4}\right)=4$

Hence, the pH of the solution becomes $4$.