1) Write the balaced chemical equation:
H2 + 2O2 → 2H2O
2) Infere the molar ratios:
1 mol H2 : 2 mol of water
3) Make the calculus as the direct proportion relation:
[2 mol H2O] / [1 mol H2] * 7 mol H2 = 14 mol H2
As you see you produce the double number of moles of H2O than number of moles of H2 used.
Answer: 14 moles
