High School Chemistry : Help with Rate-Determining Steps

Study concepts, example questions & explanations for High School Chemistry

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Example Questions

Example Question #1 : Help With Rate Determining Steps

Consider the following reaction:

The above reaction is actually composed of two steps that take place at different rates:

1.  (slow step)

2.             (fast step)

Based on this, what is the rate law for the reaction?

Possible Answers:

Correct answer:


For reactions with multiple steps, the step with the slowest rate will determine the rate law. In this reaction, the slowest step is the first step, so the reactants in that step will be the components of the rate law.

The first step is written as:

Using the reactants, we can determine the rate law to be 

Note that we cannot determine the value of the exponents, since they will need to be found experimentally.

Example Question #2 : Help With Rate Determining Steps

The overall reaction can only proceed as quickly as the __________.

Possible Answers:

catalyst is added

intermediate is decomposed

products are removed

rate-determining step

Correct answer:

rate-determining step


The rate-determining step in a reaction mechanism is a kinetic bottleneck, in that it prevents the overall reaction from proceeding; thus, it is what determines how quickly the overall reaction can proceed.

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