Find the number of equivalents of $HBr$ present in $100 \ mL$ of its solution whose $pH$ is $4$.

Equal volumes of two solutions of $pH = 3$ and $pH = 5$ are mixed. The resultant $pH$ is

The $pH$ of $10^{-5} \ M$ aqueous solution of $NaOH$ is

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)

How many litres of water must be added to $1 \ L$ of an aqueous solution of $HCl$ with a $pH$ of $1$ to create an aqueous solution with $pH$ of $2$?

Assuming complete dissociation,calculate the $pH$ of the following solutions:
$(i) \ 0.003 \ M \ HCl$
$(ii) \ 0.005 \ M \ NaOH$
$(iii) \ 0.002 \ M \ HBr$
$(iv) \ 0.002 \ M \ KOH$