Chapter 15, Problem 52E

Hydrogen sulfide is bubbled into a solution that is 0.10 M in both Pb²+ and Fe²+ and 0.30 M in HCl. After the solution has come to equilibrium it is saturated with H₂S ( ${\text{H}}_2\text{S}\left[{\text{H}}_2\text{S}\right]=0.10$M). What concentrations of Pb²+ and Fe²+ remain in the solution? For a saturated solution of H₂S we can use the equilibrium:

${\text{H}}_2\text{S}\left(aq\right)+2{\text{H}}_2\text{O}\left(l\right)\rightleftharpoons 2{\text{H}}_3{\text{O}}^{+}\left(aq\right)+{\text{S}}^{2-}\left(aq\right)$ $K=1.0\times {10}^{-26}$

(Hint: The [H₃O⁺] changes as metal sulfides precipitate.)