$A$ solution whose $pH$ value is less than $7$ will be

Find the concentration of $(OH^-)$ in a solution with $pH = 3.3$.

For an acidic solution,the $[OH^{-}]$ will be .........

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:

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

The $pH$ of a solution is $2$. If its $pH$ is to be raised to $4$,then the $[H^{+}]$ of the original solution has to be