Answer
$4 NH3(g) + 5 O2(g) --> 4 NO(g) + 6 H2O(g)$
$2 NO(g) + O2(g) --> NO2(g)$
Work Step by Step
Both of these reactions are redox reactions because at least one element in each reaction has a changing oxidation state. In other words one element undergoes oxidation, and the another element undergoes reduction.
