The atomic masses of C and O are 12 g/mol and 16 g/mol respectively.
The molar mass of CO is 12+16=28 g/mol.
56 g CO corresponds to
28
56
=2 moles.
As per balanced chemical equation, 1 mole of Fe
2
O
3
will react with 3 moles of CO.
Hence, 3.0 moles of Fe
2
O
3
will react with 3.0×3=9 moles of CO.
However only 2 moles of CO are present. Hence, CO is the limiting reagent and Fe
2
O
3
is excess reagent.
As per the balanced chemical equation, 3 moles of CO produces 2 moles of Fe.
Hence, 2 moles of CO will produce 2×
3
2
=12 g
