At $25^{\circ}C$,if the concentration of $[OH^{-}]$ is $10^{-9} \ M$,find the $pOH$ value of the solution.

What is the $pH$ of the solution containing $1.342 \times 10^{-3} \ M \ H^{+}$ ions?
$(\log 1.342 = 0.1277)$

At $100\, ^oC$,the $K_w$ of water is $55$ times its value at $25\, ^oC$. What will be the $pH$ of a neutral solution at this temperature? $(\log 55 = 1.74)$

The $pH$ of milk,black coffee,tomato juice,lemon juice and egg white are $6.8, 5.0, 4.2, 2.2$ and $7.8$ respectively. Calculate the corresponding hydrogen ion concentration $[H^+]$ in each.

If $[H^{+}]$ ion concentration of a solution is increased by $10$ times,its $pH$ will be:

If $pH$ of a solution changes from $4$ to $5$,then the $[H_3O^+]$ ion concentration of the solution: