What is the $pH$ of a solution having $H^{+}$ ion concentration $3.981 \times 10^{-7} \ M$? $(\log 3.981 = 0.6000)$

The $pH$ of a sample of vinegar is $3.76$. Calculate the concentration of hydrogen ion in it in $mol \ dm^{-3}$?

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

On adding which of the following,the $pH$ of $20 \ mL$ of $0.1 \ N \ HCl$ will not alter?

Pure water does not conduct electricity because ....

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.