Surface-nitrogen removal steps were analyzed in the course of a catalyzed NO + H-2 reaction on Pd(110) by angle-resolved mass spectroscopy combined with cross-correlation time-of-flight techniques. Four removal steps, i.e., (i) the associative process of nitrogen atoms, 2N(a) --> N-2(g), (ii) the decomposition of the intermediate, NO(a) + N(a) --> N2O(a) --> N-2(g) + O(a), (iii) its desorption, N2O(a) --> N2O(g), and (iv) the desorption as ammonia, N(a) + 3H(a) --> NH3(g), are operative in a comparable order. Above 600 K, process (i) is predominant, whereas the others largely contribute below 600 K. Process (iv) becomes significant at H-2 pressures above a critical value, about half the NO pressure. Hydrogen was a stronger reagent than CO toward NO reduction and relatively enhanced the N(a) associative process.