Statement 1: The solubility of salts of weak acid and strong base increases with increase in ${\mathrm{p}}^{\mathrm{H}}$.

Statement 2: At lower pH, equilibrium shifts in forward direction in the ionization of salt of weak acid and strong base

$\mathrm{S}={\left\{{\mathrm{K}}_{\mathrm{SP}}\frac{\left[{\mathrm{H}}^{+}\right]+\mathrm{Ka}}{\mathrm{Ka}}\right\}}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}$

Thus solubility ‘S’ increase with increase in $\left[H^{+}\right]\left(\text{or}\right)\downarrow \text{ in pH}$;

Alternate method;

$$\begin{gathered} {\mathrm{Na}}_3{\mathrm{PO}}_4\rightleftharpoons 3{\mathrm{Na}}^{+}+{\mathrm{PO}}_4^{-3}; \\ \mathrm{At} \mathrm{lower} {\mathrm{p}}^{\mathrm{H}}, \mathrm{the} {\mathrm{H}}^{+} \mathrm{added} \mathrm{removes} \mathrm{phosphate} \mathrm{ion} \mathrm{to} \mathrm{form} \mathrm{a} \mathrm{weak} \mathrm{acid}; \\ \mathrm{Equilibrium} \mathrm{shifts} \mathrm{in} \mathrm{forward} \mathrm{direction} \end{gathered}$$