Question

What is the formula for the compound iron (iii) sulfate?

Answer 1

If your're on plato it's Fe₂(SO₄)₃

Answer 2

The Iron (III) ion is
`Fe^(3+)`
The sulfate ion is
`SO _(4)^(2-)`

Thus when forming the compound iron (iii) sulfate you would need three sulfate ions bonded to two iron ions in order to fill the valency requirement

∴ the formula would be Fe₂(SO₄)₃

Whenever you are adding a number to a radical you must bracket it.