Question

A 50 ml solution of pH=1 is mixed with a 50 ml solution of pH=2. The pH of the mixture will be nearly:

• A. 0.76
• B. 1.26
• C. 1.76
• D. 2.26

Answer 1

The correct option is B 1.26

For $pH=1$, $\left[H^{+}\right]={10}^{-1}M$

Moles of $\left[H^{+}\right]={10}^{-1}\times 50\times {10}^{-3}=5\times {10}^{-3}$

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

Moles of $\left[H^{+}\right]={10}^{-2}\times 50\times {10}^{-3}=5\times {10}^{-4}$

Total moles of $\left[H^{+}\right]=55\times {10}^{-4}$

Total volume $=100ml={10}^{-1}L$

$\therefore \left[H^{+}\right]=\frac{55\times {10}^{-4}}{{10}^{-1}}=55\times {10}^{-3}$

$\therefore pH=-\log (55\times {10}^{-3})=1.26$