Suppose you had one mole of oxygen (o2). how many moles of hydrogen(h2) would react completely with oxygen, and how many moles of h2 o would be produced?
The balanced reaction that describes the reaction between hydrogen and oxygen to produce water is expressed 2H2 + O2 = 2H2O. Hence for each mole of oxygen used, two moles of hydrogen is used and two moles also of water is produced.