The mole concept helps in handling a large number of atoms and molecules in stoichiometric calculations.

1. Define 1 mole.
2. What is the number of hydrogen atoms in 1 mole of methane (CH₄) ?
3. Calculate the amount of carbon dioxide formed by the complete combustion of 80 g of methane as per the reaction:

CH_{4 (g)} + 2O_{2 (g)} ? CO_{2 (g)} + 2H₂O _(g)

(Atomic masses : C = 12.01u, H = 1.008u, O = 16u)