Answer:
2
Step-by-step explanation:
A mole is a number of particles equal to the constant of Avogrado (6,02214*10^23). So by talking about moles we are talking about a number of molecules. If we look at the reaction described 2 H2 + O2 → 2 H2O you see that two hydrogen molecules can react whit one oxygen molecule to produce two water molecules. Because a mol is a certain number of molecules it is easy to calculate around chemical reactions. So we have 4 moles of hydrogen, and two moles of oxygen. Enough building blocks to build a total of two moles of water