How many moles of $HCl$ must be removed from $1 \ L$ of an aqueous $HCl$ solution to change its $pH$ from $2$ to $3$?

Calculate the $pH$ of a $0.002 \ M$ $KOH$ solution.

When $50 \, mL$ of $0.4 \, N$ $HCl$ and $50 \, mL$ of $0.2 \, N$ $NaOH$ solutions are mixed,the $pH$ of the resulting solution will be ........

Calculate $pH$ and $pOH$ of $0.03 \ M$ $NaOH$ solution.

The $pH$ of a $0.005 \ M \ H_2SO_4$ solution will be:

$200 \ mL$ 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