A solution contains 0.036 mol L-1 Cu2+ and 0.044 mol L-1 Fe2+. A solution containing sulfide ions is added to selectively precipitate one of the metal ions from solution. At what concentration of sulfide ion will a precipitate begin to form? What is the identity of the precipitate? Ksp(CuS) = 1.3 × 10-36, Ksp(FeS) = 6.3 × 10-18.
◦ 1.4 × 10-16 mol L-1, FeS
◦ 3.6 × 10-35 mol L-1, FeS
◦ 3.6 × 10-35 mol L-1, CuS
◦ 1.4 × 10-16 mol L-1, CuS
◦ 1.4 × 10-16 mol L-1, both CuS and FeS will precipitate