We’re given the balanced reaction:

2 NO(g) + 2 H₂(g) → 2 H₂O(g) + N₂(g)

We’re being asked to calculate the average rate of the reaction with respect to N₂ and H₂O given that Δ[NO]/Δt = –19.0 M/s. Recall that the average rate of a reaction is given by:

where Δ[A] = change in concentration of reactants or products (in mol/L or M) and Δtime = change in time. We can simply do a rate-to-rate comparison based on the stoichiometric coefficients.