The $pH$ of an aqueous solution of $MgCl_2$ is .......

The aqueous solution of the following salt will have the lowest $pH$:

Repeated use of which of the following fertilizers would increase the acidity of the soil?

Which salt from the following forms an aqueous solution having $pH$ less than $7$?

At $25 \ ^\circ C$,a weak acid $HX$ has the dissociation constant $K_a = 1 \times 10^{-5}$. It forms a salt $NaX$ on reaction with an alkali. The percentage of degree of hydrolysis of a $0.1 \ M$ solution of $NaX$ is $..... \%$.

Which salt represents the highest degree of hydrolysis?