Question

How do you balance the equation NO2 + H2 →-> NH3 +H2O using the oxidation number method?

Answer 1

$NO_2 + H_2 \to NH_3 + H_2 O$

<u />$2NO_2 + 7H_2 \to 2NH_3 + 4H_2 O$

Answer 2

NO2 + H2 ----> NH3 + H2O

N(+IV) + 7e -----> N(-III) |2
H2(0) - 2e ----> 2H(+I)   |7

after:  2NO2 + 7H2 ----> 2NH3 + 4H2O