Question

100 ml of 0.1 M $H_{2}S{O}_4$ diluted 900 ml of water find the pH of resultant solution.

Answer 1

Number of moles of $H_{2}S{O}_4$ in 100 ml of 0.1 M solution
$=\frac{100mL\times 0.1mol/L}{1000mL/L}=0.01mol$
Total volume includes 100 mL of $H_{2}S{O}_4$ solution and 900 mL of water.
Total volume $=100mL+900mL=1000mL=1L$
$\left[H^{+}\right]=\frac{0.01mol}{1L}=0.01M$

$pH=-lo{g}_{10}\left[H^{+}\right]$

$pH=-lo{g}_{10}0.01$

$pH=2$