Final answer:
The suggested mechanism for the reaction NO2(g) + CO(g) → NO(g) + CO2(g) is consistent with a single-step bimolecular reaction at temperatures above 225 °C, according to the first-order rate law for both reactants. Alternative mechanisms involving intermediates can occur at different conditions.
Step-by-step explanation:
The mechanism for the reaction described by NO₂(g) + CO(g) → CO₂(g) + NO(g) can be elucidated by analyzing the reaction rate and proposing a set of elementary steps that are consistent with this rate. At temperatures above 225 °C, the experimentally determined rate law for the reaction is first order with respect to NO₂ and first order with respect to CO. This suggests a bimolecular mechanism where a collision between an NO₂ molecule and a CO molecule directly results in the formation of NO and CO₂.
However, different temperatures or conditions may result in alternative mechanisms. For example, one proposed mechanism involves the intermediate N₂O₄, with the first step being the dimerization of NO₂ to form this intermediate. The subsequent steps involve the breakdown of N₂O₄ and the reaction with CO to form the final products. The rate-determining step in a reaction mechanism is the slowest step and dictates the rate law observed experimentally. In this case, if the rate law is consistent with the bimolecular collision mechanism, then there would be no intermediate and the rate-determining step is the direct transfer of an oxygen atom from NO₂ to CO.