Question

How many grams of magnesium oxide can be produced when 125 g Mg react with 102 g O2?

Answer 1

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.