What is the $pH$ value for $\frac{N}{10} \ H_2SO_4$?

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

$0.023 \ g$ of sodium metal is reacted with $100 \ cm^{3}$ of water. The $pH$ of the resulting solution is

Five solutions of $KOH$ are prepared as follows: $1st \to 0.1 \ mol$ in $1 \ L$,$2nd \to 0.2 \ mol$ in $2 \ L$,$3rd \to 0.3 \ mol$ in $3 \ L$,$4th \to 0.4 \ mol$ in $4 \ L$,$5th \to 0.5 \ mol$ in $5 \ L$. What is the $pH$ of the resulting mixture?

Weight of $Ca(OH)_2$ needed to prepare $250 \ mL$ of solution with $pH = 13$. (in $g$)

By adding $20 \ mL$ of $0.1 \ N \ HCl$ to $20 \ mL$ of $0.001 \ N \ KOH$,the $pH$ of the resulting solution will be: