Step-by-step explanation:
You have 112 g of Fe.
The atomic mass of Fe is 56 g/mol
112g Fe/ 56g/mol = 2 mol Fe <---- you have to convert to moles of iron(iii) sulfate
From the balanced equation, you get that 2 moles of Fe react to produce 1 mole of Fe2(SO4)3
So, to convert:
2 mol Fe* (1 mol Fe2(SO4)3 / 2 mol Fe) = 1 mol Fe2(SO4)3
moles of Fe cancel and the answer is 1 mole of iron(iii) sulfate.