Question

What is the chemical formula of iron(Ill) sulfide?

Answer 1

`Fe_2S_3`; i.e. an analogue of ferric oxide, `Fe_2O_3`.

Explanation:

See this site.

Sulfur typically has a `-2` oxidation state (it is a Group VI atom, and its redox chemistry follows that of oxygen). And `Fe^(3+)`, ferric ion, has a `+3` oxidation state. We cross multiply and get the given formula.