Question

Stoichiometry: How much magnesium oxide, in grams, is produced from the reaction of 2 grams of magnesium?

Answer 1

1) Chemical equation:

Mg + O2 -> MgO

2) Balanced chemical equation:

2Mg + O2 -> 2MgO

3) Ratios

2 mol Mg : 1 mol O2 : 2 mol MgO

4) Convert 2 grams of Mg to number of moles

Molar mass of Mg: 24.3 g/mol

# of moles = grams / molar mass = 2g / 24.3 g/mol =  0.0823 mol

5) Use the theoretical ratio fo find the number of moles of MgO produced

0.0823 mol Mg *   2mol MgO / 2 mol Mg = 0.0823 mol MgO

6) Use the molar mass of MgO to obtain the quantity in grams

Molar mass of MgO = 24.3 g/mol + 16 g/mol = 40.3 g/mol

0.0823 mol MgO * 40.3 g/ mol = 3.32 g

Answer: 3.32 g