Balancing equations ?

Question

Ok, did I balance these correctly? I think they're all right, but I'm not sure about the first one. thanks!

3NaOH(aq) + Fe(NO3)3(aq) --> Fe(OH)3(s)+ 3NaNO3(aq)

NH3 --> N2 + H2

H2 + O2 --> H2O

Mg + H2SO4 --> MgSO4 + H2

Answer 1

the first & last are right,  the other

2NH3 --> N2 + 3H2

2H2 + O2 -->2H2O