2H2 + O2 ---> 2H2O
1 mole of H2 = 2g
1 mole of O2 = 32g
1 mole of H2O = 18g
according to the reaction:
2*2g H2---------------32g O2
1,6g H2----------------- x g O2
x = 12,8g O2
so reaction is stechiometric
32g O2---------------- 2*18g H2O
12,8g O2 -------------- x
x = 14,4g H2O
answer: 14,4g of water vapour