How much air is required to burn 36 g of magnesium containing 25% of this metal oxide?

1. Let’s write down the reaction equation:

2Mg + O2 = 2MgO;

2.Calculate the mass of magnesium in the sample:

m (Mg) = (1 – w (MgO) * m (sample) = 0.75 * 36 = 27 g;

3.Calculate the chemical amount of burned magnesium:

n (Mg) = m (Mg): M (Mg) = 27: 24 = 1.125 mol;

4.determine the amount of oxygen that went into the reaction:

n (O2) = n (Mg): 2 = 1.125: 2 = 0.5625 mol;

5.Calculate the volume of oxygen:

V (O2) = n (O2) * Vm = 0.5625 * 22.4 = 12.6 L;

6.The air contains 21% oxygen, we find the volume of air:

V (air) = V (O2): ϕ (O2) = 12.6: 0.21 = 60 liters.

Answer: 60 liters.