Both reactants will be completely consumed.
Take a look at the balanced chemical equation for this synthesis reaction
Notice that you have a
If you take into account the fact that both gases are under the same conditions for temperature and pressure, the aforementioned mole ratio will become volume ratio.
That is, the two gases must react in a
Here's why that is so. Assuming that you're at a pressure of 1 atm and at a temperature of
Divide these two equations to get
So, if you need a volume of hydrogen that's twice as big as the volume of oxygen, then your values confirm that both gases will be completely consumed by the reaction.
In other words,