3.6 g of magnesium was dissolved in excess of hcl. Find the volume and mass of the evolved gas.

Given:
m (Mg) = 3.6 g

To find:
m (gas) -?
V (gas) -?

Decision:
1) Write a chemical reaction:
Mg + 2HCl => MgCl2 + H2 ↑;
2) Calculate molar masses:
M (Mg) = Ar (Mg) = 24 g / mol;
M (H2) = Mr (H2) = Ar (H) * N (H) = 1 * 2 = 2 g / mol;
3) Calculate the amount of Mg substance:
n (Mg) = m (Mg) / M (Mg) = 3.6 / 24 = 0.15 mol;
4) Determine the amount of substance H2:
n (H2) = n (Mg) = 0.15 mol;
5) Calculate the mass of H2:
m (H2) = n (H2) * M (H2) = 0.15 * 2 = 0.3 g;
6) Calculate the volume of H2:
V (H2) = n (H2) * Vm = 0.15 * 22.4 = 3.36 liters.

Answer: The mass of H2 is 0.3 g; volume – 3.36 liters.