Final answer:
The reaction is second-order with respect to NO, first-order with respect to H₂, and thus third-order overall. The rate law for the reaction defines these orders based on the exponents of the reactant concentrations in the rate equation.
Step-by-step explanation:
The rate law for a reaction gives the rate of reaction as a function of the concentration of the reactants. In the question provided, the rate law for the reaction 2 NO(g) + 2 H₂(g) → N₂(g) + 2 H₂O(g) is given by Rate = k [NO]²[H₂]. Here, the exponent on [NO] indicates that the reaction is second-order with respect to NO, because the rate varies as the square of the concentration of NO. Similarly, since the concentration of H₂ is raised to the first power, the reaction is first-order with respect to H₂.
The overall order of the reaction is the sum of the exponents, which in this case is 2 + 1 = 3. Therefore, the overall reaction order is third-order. Understanding the reaction order is crucial in determining how changing concentrations of reactants will affect the rate of the reaction.