Why is the slowest elementary step "the rate determining step"?
Suppose we (you and I) are making hamburgers. You're cooking the meat and I'm toasting the buns. I can toast buns at the rate of 1 whole buns/min. You can cook a pattie in 10 minutes. What determines the number of hamburgers we can make in an hour. You of course. You can cook 6 patties in an hour while I can toast 60 whole buns in an hour. How many hamburgers can we make in an hour? Certainly not 60. More like 6 because that's as fast you can cook the meat.
Oh, I understand now!! Thank you so much :)
The slowest elementary step in a reaction is known as the rate-determining step because it controls the overall rate of the reaction. The rate of a chemical reaction is determined by the rate at which the reactants collide and undergo chemical transformations. Reactions occur in a series of steps called elementary steps, which involve the breaking and forming of chemical bonds.
In a reaction mechanism, there can be multiple elementary steps with different reaction rates. However, the overall rate of the reaction is ultimately limited by the slowest step. This is because the rate of the reaction is determined by the completion of this slowest step.
To understand why the slowest step determines the overall rate of the reaction, consider the analogy of a relay race. In a relay race, the entire team's time is determined by the slowest runner since they set the pace for the team. Similarly, in a chemical reaction, the slowest elementary step sets the pace for the overall reaction.
To identify the slowest step and hence the rate-determining step in a reaction mechanism, you can analyze the reaction's mechanism and determine the rate law for each step. The rate law expresses the relationship between the reaction rate and the concentrations of reactants. The rate-determining step typically involves the highest activation energy, which means it is the slowest step.
Understanding the rate-determining step is crucial in studying and predicting reaction rates because it helps in determining the factors that influence the overall rate of the reaction and provides insights into how to modify reaction conditions to optimize the reaction rate.