Zinc weighing 45.5 g was heated with 35.68 g NaOH. Calculate the volume of released hydrogen.

Given:
m (Zn) = 45.5 g
m (NaOH) = 35.68 g
Vm = 22.4 l / mol

To find:
V (H2) -?

Decision:
1) Zn + 2NaOH => Na2ZnO2 + H2 ↑;
2) M (Zn) = Ar (Zn) = 65 g / mol;
M (NaOH) = Mr (NaOH) = Ar (Na) * N (Na) + Ar (O) * N (O) + Ar (H) * N (H) = 23 * 1 + 16 * 1 + 1 * 1 = 40 g / mol;
3) n (Zn) = m (Zn) / M (Zn) = 45.5 / 65 = 0.7 mol;
4) n (NaOH) = m (NaOH) / M (NaOH) = 35.68 / 40 = 0.892 mol;
5) n (H2) = n (NaOH) / 2 = 0.892 / 2 = 0.446 mol;
6) V (H2) = n (H2) * Vm = 0.446 * 22.4 = 9.99 liters.

Answer: The volume of H2 is 9.99 liters.