When $100 \ mL$ of $0.1 \ M$ $NaOH$ is added to $50 \ mL$ of $0.2 \ M$ $HCl$ at $25 \ ^oC$,the $pH$ of the resulting solution will be:

Calculate the concentration of hydrogen ions $[H^+]$ in the following solutions: $(a)$ $0.001 \ M \ HNO_3$ $(b)$ $0.0001 \ M \ KOH$.

How many liters of water must be added to $1 \ L$ of an aqueous $HCl$ solution with $pH = 1$ to make the $pH$ of the resulting solution equal to $2$ (in $L$)?

The $pH$ of $100 \ mL$ of an aqueous solution of a strong acid is $1$. The volume of water to be added to change its $pH$ to $2$ is .......... $mL$.

If $0.561 \, g$ of $KOH$ is dissolved in water to give $200 \, mL$ of solution at $298 \, K$. Calculate the concentrations of potassium,hydrogen and hydroxyl ions. What is its $pH$?

Assuming that $Ba(OH)_{2}$ is completely ionised in aqueous solution under the given conditions,the concentration of $H_{3}O^{+}$ ions in $0.005 \, M$ aqueous solution of $Ba(OH)_{2}$ at $298 \, K$ is $..... \times 10^{-12} \, mol \, L^{-1}$. (Nearest integer)