I would like to know if someone could tell me if that is right:
4 H+ + 4 e− + O2 → 2 H2O
Q:How many grams of H have to react, in order to get 90g of H20?
=> First "translate" H20 into moles: 90/18=5 moles
now, I created an equation, where x stands for grams of H: x* (1mol/4g H) = 5 mole
now, we have two molecules of H20, which is why we have to divide 20/2, giving 10g of H.
Is that right?