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Homework Help: Reaction steps and Activation Energies

  1. Feb 11, 2008 #1
    1. The problem statement, all variables and given/known data

    The overall activation energy E is 60 kcal/mol.
    Reaction steps are:
    CH3CHO --> .5CH3CO + .5CH3 + .5H2 E1 = 80 kcal/mol
    CH3CO --> CH3 + CO E2 = ?
    CH3 + CH3CHO --> CH4 + CH3CO E3 = 10 kcal/mol
    CH3 + CH3CO --> minor products E4 = 5 kcal/mol

    Estimate E2.

    2. Relevant equations

    Arrhenius equation k = A exp (-E/RT)

    3. The attempt at a solution

    Does E1 + E2 + E3 + E4 = E? If so, then E2 = -35 kcal/mol. If this is the case, what does negative activation energy mean (physically)?

    Do I need to use the Arrhenius equation and/or d[M]/dt expressions to solve this problem. Since E1 >> E3 and E4, are there any assumptions I can make?

    I feel like I'm missing something here.

  2. jcsd
  3. Feb 12, 2008 #2
    I am almost positive that if you have a negative activation energy that it means that the reaction will take place and that it will not be possible to stop it.

    Hope this helps.

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