Find the mass of magnetite Fe3O4, from which it is possible to obtain iron with a mass of 5.6 g at a yield of 80%.

Let’s implement the solution:

In accordance with the condition of the problem, we write down the equation of the process:
3Fe3O4 + 8Al = 9Fe + 4Al2O3 – OBP, iron is formed (aluminothermy method);

Calculations by formulas:
M (Fe3O4) = 231.4 g / mol;

M (Fe) = 55.8 g / mol.

Let’s define the mass, quantity of the product:
W = m (practical) / m (theoretical) * 100;

m (Fe) = 5.6 / 0.80 = 7 g (theoretical weight);

Y (Fe) = m / M = 7 / 55.8 = 0.125 mol.

Proportion:
X mol (Fe3O4) – 0.125 mol (Fe);

-3 mol -9 mol from here, X mol (Fe3O4) = 3 * 0.125 / 9 = 0.04 mol.

Find the mass of the oxide:
m (Fe3O4) = Y * M = 0.04 * 231.4 = 9.256 = 9.3 g

Answer: you need magnetite weighing 9.3 g