Stoichiometry and POAC Contradiction
You applied the POAC incorrectly . Even your stoichiometric answer is incorrect.

First Balance the reaction 

$$\ce{2H2 + O2    -&gt; 2H2O}$$

We get that one mole of $\ce{O2}$ requires 2 moles of $\ce{H2}$.
Thus 10 moles $\ce{O2}$ need 20 moles of $\ce{H2}$.