The $pH$ of a solution is the negative logarithm to the base $10$ of its hydrogen ion concentration in:

The $pH$ in the stomach is approximately:

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.

$A$ beer has a $pH$ of $4.30$. What is the $[H_3O^{+}]$ concentration?

Pure water is kept in a vessel and it remains exposed to atmospheric $CO_2$ which is absorbed,then its $pH$ will be

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