Question

in what ratio H2 and O2 are present electrolysis decomposition of water

Answer 1

2H2 + O2 --> 2H2O. Two molecules of hydrogen gas (two hydrogens bonded together) are combined with one molecule of oxygen gas (two oxygen atoms bonded together) in order to form two molecules of water (two hydrogen atoms bonded to one oxygen atom).

Answer 2

Hence, when it broken it given out in ratio 2:1