Which of the following reactions yields elementary gases like N2, H2, O2, as the by products

the metals which are lower in reduction potential of electrochemical series liberate hydrogen gas in aqueous solution
2 Al + 6H2O+ 2OH−→ 2Al(OH)−4+ 3H2
Fe + H2O → FeO + H2

2 Fe + 3 H2O → Fe2O3+ 3 H2

3 Fe + 4 H2O → Fe3O4+ 4 H2

fromation of N2
NH4Cl(aq) + NaNO2(aq) → N2(g) + NaCl(aq) + 2 H2O (l)
2 NaN3→ 2 Na + 3 N2

02 fromation
photosynthesis reaction
from ozone
NaOCl +H2O2→O2+ NaCl +H2O
2KMnO4+ 3H2O2→ 2MnO2+ 2 KOH +2H2O+ 3O2