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    Reaction Mechanism Based on Rate Expression

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    Problem:
    For the reaction: 2H2(g)+2NO(g)--> N2(g)+2H2O(g)
    The observed rate expression is: rate=k[NO]^2[H2]

    Which of the following mechanisms is/are consistent with the overall reaction and the rate expression?
    a. Single step 2H2 + 2NO --> N2 + 2H2O
    b. Step 1 H2 + NO --> H2O + N (slow)
    Step 2 N + NO --> N2 + O
    Step 3 O + H2 --> H2O

    c. Step 1 H2 + 2NO --> N2O + H2O (slow)
    Step 2 H2 + N2O --> N2 + H2O

    d. Step 1 2 NO (equilibrium arrows)N2O2
    Step 2 N2O2 + H2 --> N2O + H2O (slow)
    Step 3 N2O + H2 --> N2 + H2O

    e. more than one of these mechanism (a-d) is consistent

    E is the answer to this question, but could you please include an explanation of the process, as well.

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    https://brainmass.com/chemistry/chemical-kinetics/reaction-mechanism-based-rate-expression-242718

    Solution Preview

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    The rate law is always dependent on the slowest step.

    a. Single step: 2H2 + 2NO --> N2 + 2H2O

    There is only one step, so it must be the slowest. On the reactant side, 2 H2 are used and 2 NO are used. This would suggest the rate law is R = k[H2]2[NO] 2. This ...

    Solution Summary

    This solution explains how to determine a reaction mechanism based on an overall rate expression of a reaction.

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