2Mg + O₂ = 2MgO
n(Mg)=m(Mg)/M(Mg)
n(Mg)=97.2g/24.3g/mol=4 mol
n(O₂)=m(O₂)/M(O₂)
n(O₂)=88.5 g/32.0 g/mol=2.77 mol
Mg:O₂ 2:1 4:2
4:2.77
the oxygen is in excess
the calculation for the magnesium
n(MgO)=n(Mg)
m(MgO)=n(Mg)*M(MgO)
m(MgO)=4 mol * 40.3 g/mol = 161.2 g
161.2 grams of magnesium oxide can be produced