Calculate the mass of iron and the volume of oxygen that you need to take to get 0.3 mol of iron oxide (3).

1. Let’s compose the equation of the chemical reaction:

4Fe + 3O2 = 2Fe2O3.

2. According to the reaction equation, we find the chemical amount and mass of iron, as well as the chemical amount and volume of oxygen (Vm – molar volume, constant equal to 22.4 l / mol):

n (Fe) = n (Fe2O3) * 2 = 0.3 mol * 2 = 0.6 mol.

m (Fe) = n (Fe) * M (Fe) = 0.6 mol * 56 g / mol = 33.6 g.

n (O2) = n (O2) / 2 * 3 = 0.3 mol / 2 * 3 = 0.45 mol.

V (O2) = n (O2) * Vm = 0.45 mol * 22.4 l / mol = 10.08 l.

Answer: m (Fe) = 33.6 g; V (O2) = 10.08 l.