Question

How many grams of water are produced from the reaction of 40.3 g of oxygen according to this equation? 2h2(g) + o2(g) → 2h2o(g)?

Answer 1

The balanced equation for the above reaction is as follows;
2H₂ + O₂ --> 2H₂O
stoichiometry of  O₂ to H₂O is 1:2
number of O₂ moles reacted - 40.3 g / 32 g/mol = 1.26 mol
according to molar ratio 
number of water moles produced = 2 x number of O₂ moles reacted 
number of water moles formed - 1.26 x 2 = 2.52 mol
mass of water produced = 2.52 mol x 18 g/mol = 45.4 g
45.4 g of water produced