Final answer:
To find the grams of hydrogen gas produced, use the stoichiometry of the reaction between magnesium and hydrochloric acid. For every 1 mole of magnesium used, 1 mole of hydrogen gas is produced. Therefore, if 3.0 moles of magnesium are reacted, the amount of hydrogen gas that will be produced is also 3.0 moles.
Step-by-step explanation:
To determine the grams of hydrogen gas produced, we need to use the stoichiometry of the reaction between magnesium and hydrochloric acid. From the balanced equation Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g), we can see that for every 1 mole of magnesium used, 1 mole of hydrogen gas is produced. Therefore, if 3.0 moles of magnesium are reacted, 3.0 moles of hydrogen gas will be produced.
Using the molar mass of hydrogen (1.01 g/mol), we can convert moles of hydrogen gas to grams.
3.0 moles H2 * 2.02 g/mol H2 = 6.06 g H2
So, 6.06 grams of hydrogen gas will be produced.