How much substance and what mass of oxygen is needed to obtain 240 g of MgO from magnesium?

The combustion reaction of magnesium is described by the following chemical reaction equation.

Mg + ½ O2 = MgO;

When one mole of magnesium is burned, one mole of magnesium oxide is formed. This requires half a mole of oxygen. Since there is one oxygen atom in an oxygen molecule, and two oxygen atoms in an oxygen molecule.

Let’s find the amount of the substance in 240 grams of magnesium oxide.

M MgO = 24 + 16 = 40 grams / mol;

N MgO = 240/40 = 6 mol;

The required amount of oxygen will be:

N O2 = N MgO / 2 = 6/2 = 3 mol;

Let’s find the mass of this amount of oxygen. To do this, we multiply its molar mass by the amount of substance.

M O2 = 16 x 2 = 32 grams / mol;

m O2 = 32 x 3 = 96 grams;