Question

The $pH$ of a solution is $5$. To this solution acid was added so that its $pH$ value becomes $2.0$. The increase in $H^{+}$ concentration is:

• A. $100times$
• B. $5times$
• C. $2.5times$
• D. $1000times$

Answer 1

The correct option is D $1000times$

Original $pH=5$
Original $\left[H^{+}\right]={10}^{-pH}={10}^{-5}M$
New $pH=2$
New $\left[H^{+}\right]={10}^{-pH}={10}^{-2}M$
The increase in $\left[H^{+}\right]=\frac{{10}^{-2}M-{10}^{-5}M}{{10}^{-5}M}=9.99\times {10}^2\simeq 1000$ times