Molar mass:
H₂ = 2.0 g/mol
H₂O = 18.0 g/mol
O₂ = 32.0 g/mol
2 H₂ + O₂ = 2 H₂O
2 x 2 g H₂ ------------ 2 x 18.0 g H₂O
?? H₂ ------------------ 30 g H₂O
( 30 x 2 x 2 ) / 2 x 18.0 => 120 / 36 => 3.33 g of H₂
32 g O₂ ---------- 36.0 g H₂O
?? g O₂ ----------- 30.0 g H₂O
30.0 x 32 / 36.0 => 960 / 36.0 => 26.66 g of O₂
