What percentage mass of magnesium oxide is magnesium?

When a mass of 12.7 g of magnesium is burned in air, it combines with oxygen to form magnesium oxide...?

• When a mass of 12.7 g of magnesium is burned in air, it combines with oxygen to form magnesium oxide. a) Write the chemical equation for this reaction. b) What mole ratios of reactants and products are indicated by the balanced equation? c) Determine the mass of 1 mole of each reactant and product. d) How many moles of magnesium are burned? e) How many moles of oxygen are required? f) How many moles of magnesium oxide are formed? g) How many grams of oxygen are required? h) How many grams of magnesium oxide are formed? PLEASE HELP! THANKS!

• Answer:

  a) 2 Mg + O2 → 2 MgO c) Molar mass of Mg is 24.30506 g/mol. Molar mass of O2 is 31.99886 g/mol. Molar mass of MgO is 40.30449 g/mol. d) (12.7 g Mg) / (24.30506 g/mol) = 0.523 mol Mg e) (0.523 mol Mg) x (1 mol O2/ 2 mol Mg) = 0.261 mol O2 f) (0.523 mol Mg) x (2 mol MgO / 2 mol Mg) = 0.523 mol MgO g) (0.261 mol O2) x (31.99886 g O2/mol) = 8.35 g O2 h) (0.523 mol MgO) x (40.30449 g MgO/mol) = 21.1 g MgO