How many liters of hydrogen are formed if the amount of calcium is 0.2 mol?

Given:
n (Ca) = 0.2 mol

To find:
V (H2) -?

Decision:
1) First of all, it is necessary to draw up the equation of the chemical reaction:
Ca + 2HCl => CaCl2 + H2 ↑;
2) Focusing on the amount of Ca substance, it is necessary to determine the amount of H2 substance (taking into account the coefficients in the chemical reaction equation):
n (H2) = n (Ca) = 0.2 mol;
3) Finally, calculate the volume of H2 that is formed during the reaction (under normal conditions):
V (H2) = n (H2) * Vm = 0.2 * 22.4 = 4.48 liters.

Answer: The volume of H2 is 4.48 liters.