Calculate the mass of aluminum that will be required to obtain 5.6 g of silicon from its oxide.

To solve, we write the equation:
3SiO2 + 4Al = 2Al2O3 + 3Si – OBP, silicon was obtained by the method of aluminothermy;
Let’s calculate the molar masses:
M (Al) = 26.9 g / mol;
M (Si) = 28 g / mol.
Determine the amount of moles of aluminum, silicon:
Y (Si) = m / M = 5.6 / 28 = 0.2 mol;
X mol (Al) – 0.2 mol (Si);
-4 mol – 3 mol from here, X mol (Al) = 4 * 0.2 / 3 = 0.26 mol.
We find the mass of the metal – Al by the formula:
m (Al) = Y * M = 0.26 * 26.9 = 6.99 g.
Answer: the reaction requires aluminum weighing 6.99 g.