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

Statement-$I$ :- $pH$ of pure water increases with increase in temperature.
Statement-$II$ :- Degree of ionisation increases with increase in temperature.

What is the concentration of $[H^+]$ in a solution with a $pH$ of $5.4$?

At $25 \, ^\circ C$,the $pH$ value of a solution is $6$. The solution is:

At a certain temperature,if $pK_w = 12.60$,then which of the following is correct for an acidic solution?

Observe the following solutions:
$I$. Black coffee
$II$. $0.2 \ M \ NaOH$
$III$. Lemon juice
$IV$. Lime water
$V$. Human saliva
$VI$. Tomato juice
The number of solutions having $pH$ range of $1-7$ and $7-14$,in the above list,is respectively.