Zinc at high temperatures reacts with steam to form zinc oxide and hydrogen.

Zinc at high temperatures reacts with steam to form zinc oxide and hydrogen. Calculate: a) volume; b) the number of hydrogen molecules formed by the interaction of 13 g of zinc with water vapor.

Given:
m (Zn) = 13 g
Vm = 22.4 l / mol
NA = 6.02 * 10 ^ 23 mol − 1

To find:
V (H2) -?
N (H2) -?

Decision:
1) Write the equation of a chemical reaction:
Zn + H2O => ZnO + H2 ↑;
2) Calculate the amount of substance Zn:
n (Zn) = m (Zn) / M (Zn) = 13/65 = 0.2 mol;
3) Determine the amount of substance H2:
n (H2) = n (Zn) = 0.2 mol;
4) Calculate the volume H2:
V (H2) = n (H2) * Vm = 0.2 * 22.4 = 4.48 l;
5) Calculate the number of H2 molecules:
N (H2) = n (H2) * NA = 0.2 * 6.02 * 10 ^ 23 = 1.2 * 10 ^ 23.

Answer: The volume of H2 is 4.48 liters; the number of molecules is 1.2 * 10 ^ 23.