I assume there is a typo in the equation. It is H2O instead of H2I.
The ratio of H2 and O2 that react with each other is 2:1. To find out the grams of H2, we need to first find out the moles of O2 and H2.
Moles of O2 = mass of O2/molar mass of O2 = 192g/32g/mol = 6 mol. Therefore, the moles of H2 = 6mol *2 = 12 mol.
So the mass of H2 that reacts with O2 = moles of H2 * molar mass of H2 = 12 mol * 2 g/mol = 24 g
