The steady-state reaction of NO with H-2 and NH3 on Pt(100) is investigated over a temperature range of 340-570 K, and the rotational and vibrational states of the N-2 product are probed by resonance enhanced multiphoton ionization. For NO + NH3 the N-2 reaction product leaves the surface rotationally and vibrationally excited, whereas for NO + H-2, the desorbing N-2 is rotationally equilibrated with the surface and no vibrational excitation can be detected. We conclude that although these two surface reactions both yield N-2, the actual reaction mechanisms must be different.