Question

The $pH$ of an $HCl$ solution is 2.0. The sufficient water is added to it to make the $pH$ of the new solution 5.0. The $H^{+}$ ion concentration is reduced:

• A. ten fold
• B. seven fold
• C. thousand fold
• D. hundred fold

Answer 1

The correct option is C thousand fold

$pH=2$ so $\left[H^{+}\right]={10}^{-2}$

$pH=5$ so $\left[H^{+}\right]={10}^{-5}$

If we want to make the $pH$ of $5$ than,

$\left[H^{+}\right]$ reduced$=\frac{{10}^{-2}}{{10}^{-5}}={10}^3$

Thousand Folds.