What is a mole ratio?
The mole ratio is the ratio of moles of one substance to the moles of another substance in a balanced equation.
2 H2(g) + O2(g) → 2 H2O(g)
The mole ratio between O2 and H2O is 1:2. For every 1 mole of O2 used, 2 moles of H2O are formed.
The mole ratio between H2 and H2O is 1:1.
For every two moles of H2 used, 2 moles of H2O is formed.