Rate Determining Step: Explained & Contradicted

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In summary, the fast step in a reaction is often ignored when determining the rate law because it depends on the slower step and does not have a significant impact on the overall rate of the reaction.
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If a slow elementary reaction between two colliding species takes 2 s, and a fast step afterwards takes 1 s the total time is 3 s. Since the time for the overall reaction's completion is increased by the fast step, why is it ignored in determining the rate law? Thanks,

P.S. This is not a homework question, this is an example I thought of that seems to contradict the use of the rate determining step.
 
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Because the faster step depends on the slower step.

The faster step will consume the products of the slower step faster than new products are being made. Because of this, the faster step has no real effect on the rate.
 
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1. What is a rate determining step?

A rate determining step is the slowest step in a chemical reaction that determines the overall rate of the reaction. It is also known as the "rate-limiting step".

2. How do you identify the rate determining step?

The rate determining step can be identified by looking at the reaction mechanism. The step with the highest activation energy is usually the rate determining step. This can also be determined experimentally by varying the concentrations of reactants and observing the effect on the reaction rate.

3. Can the rate determining step change?

Yes, the rate determining step can change depending on the reaction conditions. For example, a different step may become the rate determining step if the temperature or concentration of reactants is changed.

4. How does the rate determining step affect the overall reaction rate?

The rate determining step sets the pace for the entire reaction. If it is slow, the overall reaction rate will be slow. This is because all other steps in the reaction cannot proceed faster than the rate determining step.

5. Is the rate determining step always the first step in a reaction?

No, the rate determining step can occur at any point in the reaction mechanism. It is not always the first step, but it is often the slowest step.

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