Sulfur Can Be Separated from Lead in the Mineral Galena $\to$

Short Answer

Sulfur can be separated from lead in the mineral galena, PbS(s), by "roasting" the ore in the presence of oxygen as shown in the following reaction:
2PbS(s)+ 3O₂(g) $\to$ 2PbO(s)+ 2SO₂(g)
Determine $\Delta$ G for the above reaction at 850°C.