Question

Given STP conditions, how many milliliters of hydrogen gas are produced by the reaction 0.020 mol of magnesium with excess of hydrochloric acid?

Answer 1

The balanced equation for the reaction of magnesium and hydrochloric acid is,
Mg + 2HCl ---> H2 + MgCl2
From the reaction, every 0.02 moles of magnesium will produce 0.02 moles H2. Using the ideal gas equation,
V = nRT / P
Substituting the known values,
V = (0.02 mol)(0.0821 L.atm / mol K)(273 K) / 1 atm
= 0.45 L = 450 mL
Therefore, the hydrogen gas produced is approximately 450 mL.