<u>Answer:</u> The hydrogen gas is the limiting reagent and 6 molecules of water are produced.
<u>Explanation:</u>
We are given:
Molecules of hydrogen gas = 6 molecules
Molecules of oxygen gas = 6 molecules
The chemical equation for the reaction of hydrogen gas and oxygen gas follows:

By Stoichiometry of the reaction:
2 molecules of hydrogen gas reacts with 1 molecule of oxygen gas
So, 6 molecules of hydrogen gas will react with =
molecules of oxygen gas
As, given amount of oxygen gas is more than the required amount. So, it is considered as an excess reagent.
Thus, hydrogen gas is considered as a limiting reagent because it limits the formation of product.
By Stoichiometry of the reaction:
2 molecules of hydrogen gas produces 2 molecules of water
So, 6 molecules of hydrogen gas will produce =
molecules of water
Hence, the hydrogen gas is the limiting reagent and 6 molecules of water are produced.