Calculate the volume of air required to burn 120 g of coal.

1. Let’s compose the reaction equation:

C + O2 = CO2;

2. find the chemical amount of carbon:

n (C) = m (C): M (C) = 12: 120 = 0.1 mol;

3.According to the reaction equation, the amounts of carbon and oxygen are the same:

n (O2) = n (C) = 0.1 mol;

4. find the volume of oxygen:

V (O2) = n (O2) * Vm = 0.1 * 22.4 = 2.24 dm3;

5.The air contains 21% oxygen, we determine the volume of air:

V (air) = V (O2): ϕ (O2) = 2.24: 0.21 = 10.67 dm3.

Answer: 10.67 dm3.