The balanced equation is as follows;
2H₂ + O₂ ---> 2H₂O
the mass of water molecules formed - 1.8 g
Therefore number of water molecules produced - 1.8 g / 18 g/mol = 0.1 mol
Stoichiometry of H₂ to H₂O is 2:2
therefore number of hydrogen moles reacted = number of water moles formed
number of H₂ moles produced - 0.1 mol
therefore mass of H₂ - 0.1 mol x 2 g/mol = 0.2 g
