What will be the $pH$ value of $0.05 \, M$ $Ba(OH)_2$ solution?

Number of equivalents of $H_2SO_4$ present in $100 \ mL$ of its solution whose $pH$ is $5$.

$200 \ mL$ of an aqueous solution of $HCl$ $(pH=2)$ is mixed with $300 \ mL$ of aqueous solution of $NaOH$ $(pH=12)$ and is diluted to $1.0 \ L$. The $pH$ of the resulting solution is

If $1 \ mL$ of $1 \ M \ HCl$ solution is added to $99 \ mL$ of aqueous solution of $NaCl$,the $pH$ of the solution changes by $X$ units. The value of $X$ is:

The $pH$ of a $0.001 \, M$ solution of $HCl$ is:

The $pH$ of $1 \ L$ of an aqueous solution of $HCl$ is $1$. How many liters of water must be added to make the $pH$ of this solution $2$ (in $L$)?