Question

If $100mL$ of $pH=3$ and $400mL$ of $pH=3$ is mixed, what will be the pH of the mixture?

• A. $3.2$
• B. $3.0$
• C. $3.5$
• D. $2.8$

Answer 1

The correct option is B $3.0$

$\therefore$ Both the solutions are acidic so,

$\left[H^{+}\right]=\frac{N_1{V}_1+N_2{V}_2}{V_1+V_2}$

$\left[H^{+}\right]=\frac{{10}^{-3}\times 100+{10}^{-3}\times 400}{100+400}=\frac{0.5}{500}M={10}^{-3}M$

$pH=-\log \left[H^{+}\right]=3$