What mass of magnesium enters into reaction with sulfuric acid Н2SO4

What mass of magnesium enters into reaction with sulfuric acid Н2SO4, if as a result of the reaction 5.6 liters of hydrogen Н2 are released under normal conditions?

Given:
V (H2) = 5.6 L

To find:
m (Mg) -?

Decision:
1) Mg + Н2SO4 => MgSО4 + Н2;
2) n (H2) = V (H2) / Vm = 5.6 / 22.4 = 0.25 mol;
3) n (Mg) = n (H2) = 0.25 mol;
4) m (Mg) = n (Mg) * M (Mg) = 0.25 * 24 = 6 g.

Answer: The mass of Mg is 6 g.