This sequence describes the formation of sulfur dioxide gas (SO2) from iron metal (Fe) through a series of chemical reactions:

Iron metal (Fe) reacts with sulfur (S) to form iron sulfide (FeS).Iron sulfide (FeS) reacts with hydrogen sulfide gas (H2S) to form potassium sulfide (K2S) and release hydrogen gas (H2).Potassium sulfide (K2S) reacts with acid to release hydrogen sulfide gas (H2S).Hydrogen sulfide gas (H2S) reacts with sulfur (S) to release hydrogen gas (H2) and form sulfur.Sulfur reacts with oxygen gas to form sulfur dioxide gas (SO2).