19. Identify each of the following elementary reactions as unimolecular, bimolecular, or termolecular, and write the rate expression.
(a) HCO + O2 ---> HO2 + CO
Bimolecular; r = k[HCO][O2]
(b) CH3 + O2 + N2 ---> CH3O2 + N2
Termolecular; r = k[CH3][O2][N2]
(c) HO2NO2 ---> HO2 + NO2
Unimolecular; r = k[HO2NO2]