Calculate the concentration in a saturated () solution to which enough has been added to produce a s — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

For a diprotic acid like $H_2S$, the overall dissociation constant is $K = K_1 \times K_2 = \frac{[H^+]^2[S^{2-}]}{[H_2S]}$. Rearranging for $[S^{2-}]$, we get $[S^{2-}] = \frac{K_1 K_2 [H_2S]}{[H^+]^2}$. Substituting the known values: $[S^{2-}] = \frac{10^{-7} \times 10^{-14} \times 0.1}{(2 \times 10^{-4})^2} = \frac{10^{-22}}{4 \times 10^{-8}} = 0.25 \times 10^{-14} = 2.5 \times 10^{-15} \text{ M}$.