Calculate the volume of air required to burn 36 g of magnesium. (recall that the volume fraction of oxygen in air is 0.21)

Metallic magnesium is intensively oxidized by oxygen. This reaction is described by the following equation:
Mg + ½ O2 = MgO;
During oxidation, 1 oxygen atom is attached to the magnesium atom and 1 molecule of magnesium oxide is synthesized.
Find the molar amount of magnesium.
To do this, divide the available weight of magnesium by the weight of 1 mole of this substance.
M Mg = 24 grams / mol; N Mg = 36/24 = 1.5 mol;
To oxidize this amount of magnesium, 2 times less chemical amount of oxygen is required.
Let’s calculate the gas volume. To do this, multiply the volume of oxygen by the volume of 1 mole, which is 22.4 liters.
V O2 = 1.5 / 2 x 22.4 = 16.8 liters;
The air volume will be.
V air = V O2 / 0.21 = 16.8 / 0.21 = 80 liters;