An aqueous solution contains 0.10 M ${\mathrm{H}}_2\mathrm{S}$ and 0.20 M HCl. If the equilibrium constants for the formation of $\mathrm{H}{\mathrm{S}}^{–}$ from ${\mathrm{H}}_2\mathrm{S}$ is $1.0\times 10^{-7}$ and that of ${\mathrm{S}}^{2-}$ from $\mathrm{H}{\mathrm{S}}^{-}$ ions is $1.2\times 10^{-13}$ then the concentration of ${\mathrm{S}}^{2-}$ ions in aqueous solution is