Calculate the volume of gas that forms when zinc reacts with solutions containing 0 and little hydrochloric acid.

Given:
n (HCl) = 0.4 mol

To find:
V (gas) -?

1) Write the equation of a chemical reaction:
Zn + 2HCl => ZnCl2 + H2 ↑;
2) Determine the amount of hydrogen substance (taking into account the coefficients in the reaction equation):
n (H2) = n (HCl) / 2 = 0.4 / 2 = 0.2 mol;
3) Calculate the volume of hydrogen (under normal conditions):
V (H2) = n (H2) * Vm = 0.2 * 22.4 = 4.48 liters.

Answer: The volume of gas (hydrogen) is 4.48 liters.