Question

In a solution of $pH=5$,more acid is added in order to reduce the $pH=2$. the increase in hydrogen ion concentrations is:

• A. $100$ times
• B. $1000$ times
• C. $3$ times
• D. $5$ times

Answer 1

The correct option is B $1000$ times

The $pH$ is equal to $-{\log }_{10}\left[H^{+}\right]$ where $\left[H^{+}\right]$ is the hydrogen ion concentration in mol/litre.

At $pH=5,\left[H^{+}\right]={10}^{-5}mol/L$

At $pH=2,\left[H^{+}\right]={10}^{-2}mol/L$

Hydrogen ion concentration is increased by $\frac{{10}^{-2}}{{10}^{-5}}\Rightarrow {10}^{-2+5}={10}^3$

$\Rightarrow 1000$ times