Calculate the concentration of $H_3O^{+}$ ion if the $pH$ of the solution is $2.8$.

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.

The $pH$ of $1 \ N \ H_2O$ is

At $298 \, K$,the equivalent conductivity of a $0.01 \, M$ solution of aniline hydrochloride is $122.5 \, \Omega^{-1} \, cm^2 \, eq^{-1}$,but in the presence of a sufficient excess of aniline to prevent hydrolysis,it is $106.5 \, \Omega^{-1} \, cm^2 \, eq^{-1}$. The equivalent conductivity of $HCl$ at infinite dilution is $426.0 \, \Omega^{-1} \, cm^2 \, eq^{-1}$. The hydrolysis constant of aniline is:

The $pH$ of rain water is approximately

The concentration of hydrogen ion in a sample of soft drink is $3.8 \times 10^{-3} \ M$. What is its $pH$ (in $.42$)?