The concentration of hydrogen ion in a sample solution is $4.7 \times 10^{-4} \ M$. Find its $pH$.

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

The $pH$ of water is $7$ at $25^{\circ} C$. If water is heated to $80^{\circ} C$,its $pH$ will:

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 with $pH$ less than $7$ is

The $[H^{+}]$ in lemon juice is found to be $0.0063 \ M$. What is the $pH$ value of lemon juice? $(\log 6.3 = 0.7993)$

When pure water is taken in a container and it absorbs $CO_2$ from the atmosphere,what will be the $pH$?