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Kinetics

Rate Equations and Reaction Mechanisms

  • 3 things to know
  • Papers 2 and 3

Overview

The rate-determining step, and what a species appearing in the rate equation tells you.

What you need to know

Answer each one before you reveal it.

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Key term

What is the rate-determining step of a reaction?

Key term

How does the rate-determining step relate to the overall rate equation?

Process

If a species appears in the rate equation, what can be concluded about its involvement in the mechanism?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the rate-determining step of a reaction?

    Model answer

    The slowest step in a multi-step reaction mechanism

  2. 2

    How does the rate-determining step relate to the overall rate equation?

    Model answer

    The rate equation reflects only the species involved in the rate-determining step and any steps before it

  3. 3

    If a species appears in the rate equation, what can be concluded about its involvement in the mechanism?

    Model answer

    The species is involved in the rate-determining step or in a step before it

  4. 4

    If a species does not appear in the rate equation, what does this indicate about when it is involved in the mechanism?

    Model answer

    The species is involved in a step after the rate-determining step

  5. 5

    What is the relationship between the order of a reactant in the rate equation and the number of molecules of that reactant in the rate-determining step?

    Model answer

    The order with respect to a reactant equals the number of molecules of that reactant involved in the rate-determining step

  6. 6

    A reaction has the rate equation rate = k[A][B]. What does this suggest about the rate-determining step?

    Model answer

    The rate-determining step involves one molecule of A and one molecule of B

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