Calculate the volume of hydrogen that is released if magnesium reacts with a solution

Calculate the volume of hydrogen that is released if magnesium reacts with a solution of orthophosphoric acid with an amount of substances of 1 mol.

Reaction equation:
2H3PO4 + 3Mg = Mg3 (PO4) 2 + 3H2.
3 mol of Mg enters the reaction and the same mol of hydrogen is formed, which means:
V (H2) = Vm * n = 22.4 l / mol * 3 mol = 67.2 l.
From 1 mol of magnesium, xl of hydrogen is formed, we get the ratio:
1 mol Mg – X l H2.
3 mol Mg – 67.2 l H2.
V (H2) = 1 * 67.2 / 3 = 22.4 liters.