Answer:
It takes 7 mol H2 to produce 7 mol H2O
Explanation:
In 2H2O, there's 2 moles of H2 for every 1 mol O2.
So, if oxygen is limiting you'd only be able to produce 2 moles of H2O. I don't know if the question implies that, so it could also be that 7 mol H2 makes 7 mol H2O. Sorry for the confusion, I hope it helps a bit
