The balanced chemical reaction is
2Mg + O2 → 2MgO
To determine the amount of magnesium oxide produced from the reaction, we use the initial amount of the reactants and the relation of the substances from the reaction. We do as follows:
125 g Mg ( 1 mol / 24.31 g ) = 5.14 mol Mg
102 g O2 ( 1 mol / 32 g) = 3.19 mol O2
Therefore, the limiting reactant is magnesium. We calculate as follows:
5.14 mol Mg ( 2 mol MgO / 2 mol Mg ) ( 40.31 g /mol) = 207.19 g MgO produced.
