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Homework Help: Need help help on reaction mechanism

  1. May 25, 2009 #1
    1. For the reaction

    2NO + Cl2 --> 2NOCl

    Match the appropriate rate law to each postulated mechanism.
    A Rate = k[NO]2[Cl2]2
    B Rate = k[NO][Cl2]
    C Rate = k[NO][Cl2]2
    D Rate = k[Cl2]
    E Rate = k[Cl2]2
    F Rate = k[NO]
    G Rate = k[NO]2[Cl2]
    H Rate = k[NO]2
    I None of the above

    NO + Cl2 --> NOCl2 slow
    NOCl2 + NO ---> 2NOCl fast

    2NO --> N2O2 slow
    N2O2 + Cl2 --> 2NOCl fast

    NO + Cl2 NOCl2 ---> fast equilibrium
    2NOCl2 NOCl3 + NOCl ---> slow
    NOCl3 ---> NOCl + Cl2 fast

    NO + Cl2 ---> NOCl2 fast equilibrium
    NOCl2 + NO ---> 2NOCl slow

    i have no idea where to start. book isn't very helpful. basically, you look at the slow reaction then you subisitute the intermediate for the fast reaction. But i dont know what i do next. Do i cancel or what?

    2. 5Br-(aq) + BrO3-(aq) + 6H+(aq) 3Br2(l) + 3H2O(l)

    The above reaction is expected to obey the mechanism:

    BrO3-(aq) + H+(aq) <-->HBrO3(aq) Fast equilibrium
    HBrO3(aq) + H+(aq) <---> H2BrO3+(aq) Fast equilibrium
    H2BrO3+(aq) + Br-(aq) <---> (Br-BrO2)(aq) + H2O(l) Slow
    (Br-BrO2)(aq) + 4H+(aq) + 4Br-(aq) <---> products Fast

    For each of the given rate expressions choose the correct expression for the rate constant (k)

  2. jcsd
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