Since this is a single replacement reaction, the equation for the reaction is:
[tex]\text{Mg}+\text{H}_{2}\text{SO}_{4} \longrightarrow \text{MgSO}_{4}+\text{H}_{2}[/tex]
From this, we know that for every mole of magnesium consumed, 1 mole of hydrogen is produced.
The atomic mass of magnesium is 24.305 g/mol, so 72 grams of magnesium is 72/24.305 = 2.9623534252211 moles.
This means we need to find the mass of 2.9623534252211 moles of hydrogen.
Hydrogen has an atomic mass of 1.00794 g/mol, so doubling this to get the formula mass of of [tex]\text{H}_{2}[/tex], we get 2.01588 g/mol, which his a mass of:
(2.01588)(2.9623534252211). which is about 5.97 g
