What is the $pOH$ of a $1 \ mM$ solution of $Ca(OH)_2$?

Water is added to $1.0 \ mL$ of $0.1 \ M$ $HCl$ solution to make the total volume $50 \ mL$. Calculate the $pH$ change of the solution.

$200 \ mL$ 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

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?

Calculate the volume of $0.1 \ M \ NaOH$ required to complete the neutralization of $300 \ mL$ of $HCl$ solution having $pH = 2.25$. (in $mL$)

The $pH$ of a solution obtained by mixing $10 \ mL$ of $0.1 \ M$ $HCl$ and $40 \ mL$ of $0.2 \ M$ $H_2SO_4$ is (Given $\log 17 = 1.23, \log 5 = 0.7, \log 10 = 1$)