$pH$ of a solution is $5$. Its hydroxyl ion concentration is

When $NaCl$ is dissolved in water,the sodium ion becomes

There are two different solutions, $A$ and $B$. The $pH$ of solution $A$ is $4$. Find the $pH$ of solution $B$ having $[H^+]$ concentration three times that of solution $A$.

If the $pH$ of a solution is $2$,find the $[H^{+}]$ of the solution.

The number of $H^{+}$ ions present in $10 \ mL$ of a solution with $pH = 12$ is ........

$2$. Given below are two statements:
Statement $I$: The changes in $pH$ with temperature are so small that we often ignore them.
Statement $II$: When the hydrogen ion concentration changes by a factor of $100$,the $pH$ changes by one unit.
In the light of the above statements,identify the correct answer from the options given below: