The $pH$ value of a decinormal solution of $NH_4OH$ which is $20\%$ ionised,is

If $10\%$ of a $5 \times 10^{-3} \, M \, H_2CO_3$ solution dissociates,then the concentration of $H^{+}$ ions is equal to $......$.

Estimate the approximate $pK_a$ of $0.5 \ M$ $CH_3COOH$. Degree of dissociation (ionisation) is $0.15$ $(\log 1.32 = 0.12)$.

If the degree of dissociation of formic acid is $11.0 \%$,the molar conductivity of $0.02 \ M$ solution of it is (Given: $\lambda^{\circ}(H^{+}) = 349.6 \ S \ cm^2 \ mol^{-1}, \lambda^{\circ}(HCOO^{-}) = 54.6 \ S \ cm^2 \ mol^{-1}$)

The pairs of compounds which cannot exist together in aqueous solution are :
$I. NaH_2PO_4$ and $Na_2CO_3$ $II. Na_2CO_3$ and $NaHCO_3$
$III. NaOH$ and $NaH_2PO_4$ $IV. NaHCO_3$ and $NaOH$

Calculate the ionic product of the solution formed by mixing equal volumes of $0.004 \, M \, CaSO_4$ and $0.002 \, M \, H_2SO_4$.