An acidified solution of $0.05 \mathrm{M} \mathrm{Zn}^{2+}$ is saturated with $0.1 \mathrm{M} \mathrm{H}_2 \mathrm{~S}$. What is the minimum molar concentration $(\mathrm{M})$ of $\mathrm{H}^{+}$required to prevent the precipitation of ZnS ? Use $K_{\mathrm{sp}}(\mathrm{ZnS})=1.25 \times 10^{-22}$ and Overall dissociation constant of $\mathrm{H}_2 \mathrm{~S}, K_{\mathrm{NET}}=K_1 K_2=1 \times 10^{-21}$