8g of hydrogen is burnt in the presence of excess oxygen.the mass of water formed is?

Answer 1

2H2 + O2 ==> 2H2O
mols H2 = grams/molar mass H2 = ?
mols H2 x 1 = mols H2O
grams H2O = mols H2O x molar mass H2O

Answer 2

40g