80 g of technical zinc contains 20% of impurities reacted with sulfuric acid. Find the volume of gas released

Let’s write the reaction equation:
Zn + H2SO4 = ZnSO4 + H2 ↑

Let’s find the amount of zinc substance:
ω (pure zinc) = 100% – 20% = 80% = 0.8

m (Zn) = m (technical zinc) * ω (pure zinc) = 80 * 0.8 = 64 g

n (Zn) = m (Zn) / Mr (Zn) = 64/65 = (about) 0.985 mol;

Let’s find the volume of released hydrogen:
n (H2) = n (Zn) = 0.985 mol;

V (H2) = n (H2) * Vm = 0.985 * 22.4 = (approximately) 22.1 L

Answer: 22.1 liters.