Show that the two reactions can be summed to give the

Question

The oxidation of SO2 to SO3 is catalyzed by NO2. The reaction proceeds according to:

NO2(g) + SO2(g) → NO(g) + SO3(g)

2NO(g) + O2(g) → 2NO2(g)

(a) Show that the two reactions can be summed to give the overall oxidation of SO2 by O2 to give SO3.

(b) Why do we consider NO2 a catalyst and not an intermediate in this reaction?

(c) Is this an example of homogeneous catalysis or heterogeneous catalysis?