If i need 2.2 moles of co2 , and i have excess fe2o3 , how many moles of c do i need?

2fe2o3 + c --> fe + 3co2

0.733 mol.

Explanation:

2Fe₂O₃ + C → Fe + 3CO₂,

It is clear that 1.0 moles of Fe₂O₃  react with 1.0 mole of C to produce 1.0 mole of Fe and 3.0 moles of CO₂.

Using cross multiplication:

1.0 mole of C produces → 3.0 moles of CO₂, from the stichiometry.

??? mole of C produces → 2.2 moles of CO₂.

∴ The no. of moles of C needed to produce 2.2 moles of CO₂ = (1.0 mole of C) (2.2 mole of CO₂) / (3.0 mole of CO₂) = 0.733 mol.