In a saturated solution of $Mg(OH)_2$,the degree of dissociation of $Mg(OH)_2$ is $\alpha$. Find the concentration $(C)$ of $Mg(OH)_2$ if the concentration of $[OH^{-}]$ is $2$.

The moles of $H^{+}$ from $H_2O$ alone in a $1 \ L$,$\sqrt{5} \times 10^{-7} \ M$ $HCl$ solution at $25 \ ^\circ C$ is ( $\sqrt{5} = 2.23$ )

$A$ $20 \ mL$ sample of a $0.2 \ M$ solution of the weak diprotic acid $H_2A$ is titrated with $0.25 \ M \ NaOH$. Molarity of the solution at the second equivalence point is:

Given,$pH$ of a solution $A$ is $3$ and it is mixed with another solution $B$ having $pH$ $2$. If both are mixed in equal volume,then the resultant $pH$ of the solution will be

Given below are two statements :
Statement $I$ : Aqueous solution of ammonium carbonate is basic.
Statement $II$ : Acidic/basic nature of salt solution of a salt of weak acid and weak base depends on $K_a$ and $K_b$ value of acid and the base forming it.
In the light of the above statements,choose the most appropriate answer from the options given below :

At $25^{\circ} C$, the molar conductance of $0.007 \ M$ hydrofluoric acid is $150 \ \text{mho} \ cm^{2} \ mol^{-1}$ and its $\Lambda_{m}^{\circ} = 500 \ \text{mho} \ cm^{2} \ mol^{-1}$. The value of the dissociation constant of the acid at the given concentration at $25^{\circ} C$ is