How does the rate-determining step affect the measured rate of a reaction?

The measured rate of a reaction closely corresponds to the rate of the rate-determining step because this step is the slowest step in the reaction mechanism and therefore limits the overall speed of the reaction. In a multi-step reaction, some steps may occur rapidly, but the rate-determining step represents the bottleneck that the reaction must pass through. As a result, changes to the conditions or concentration of reactants will most significantly affect the rate of this slowest step, subsequently influencing the measured rate of the entire reaction.

Since the rate-determining step controls the pace at which the entire reaction proceeds, the overall rate will reflect the kinetics of this specific step more than any other fast steps involved in the mechanism. This is why understanding the rate-determining step is crucial in reaction kinetics. Factors such as temperature, catalysts, and the concentration of reactants will primarily affect the measured rate because they influence this pivotal step directly.