In which reaction does Hydrogen behave as an oxidising agent?

0 0 +1 -1

1)H_{2 }+ Cl_{2} --> 2HCl

+2 -1 0 +3 -1

2)C_{2}H_{4} + H_{2} --> C_{2}H_{6}

0 0 +3 -1

3)N_{2 }+ 3H_{2 }--> 2NH_{3}

0 0 +1 -1

4)2Na + H_{2 }--> 2NaH

In the second equation, oxidation number of H in H_{2} (0) decreases to -1 in C_{2}H_{6, }while oxidation number of C in C_{2}H_{4} (+2) increases to +3 in C_{2}H_{6. }Isn't H an oxidising agent in this case? The answer given is the last equation, which is also correct. I'm confused. Isn't equation 2 valid too?

## In equation 2, the oxidation

In equation 2, the oxidation number of hydrogen is +1, and that of carbon is -2 in C2H4, and -3 in C2H6.

The reason for this is the electronegativity of C is 2.4 and that of H is 2.1. That is why equation 4 is the correct answer.