If the rate law for an elementary reaction is second order, we can conclude that

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The rate law for an elementary reaction reflects the molecularity of the reaction, which is determined by the number of molecules or particles that collide to form the activated complex. For a second-order reaction, the reaction must involve a collision between two molecules (or particles, such as ions) because the rate law expresses the dependence of the reaction rate on the concentration or pressure of two reactants. Catalysts or intermediates can be involved in the reaction, but they do not affect the overall molecularity of the reaction. Additional experiments may not be necessary to determine the molecularity because it can be inferred from the rate law. The reaction is not necessarily unimolecular because unimolecular reactions have a first-order rate law.

If the Rate Law for an Elementary Reaction Is Second