Calculate the volume of air required to burn 50 g of calcium.

1. Let’s compose the equation of calcium combustion:

2 Ca + O2 = 2 CaO

According to the equation, the following enter into the reaction:

2 mol calcium;
1 mole of oxygen.
Let’s find the mass of calcium by the formula:

m (Ca) = n * M = 2 mol * 40 g / mol = 80 g

Let’s find the volume of oxygen by the formula:

V (O2) = Vm * n = 22.4 L / mol * 1 mol = 22.4 L

2. Let’s calculate the volume of oxygen, making up the proportion:

50 g Ca – xl O2

80 g Ca – 22.4 L O2

Hence, x = 50 * 22.4 / 80 = 14 l

3. Let’s calculate the volume of air, knowing that it contains 20% O2:

14 l O2 – 20%

xl of air – 100%

Hence, x = 14 * 100/20 = 70 liters.