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Rate constant

Discussion in 'DAT Discussions' started by peyman2002, Dec 23, 2008.

  1. peyman2002

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    Just making sure here, catalysts dont change the rate constant, agree?
    only temp does. Im asking this cause one of the questions on examkracker's chem book asks about the rate constant and in the explanation part the answer says that K IS dependent on catalysts. I dont think thats right.


    catalysts only change the rate of the rxn not K
     
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  3. zuma35

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    Catalysts do not change the equilibrium constant, but they DO change the rate constant.
     
  4. Danny289

    Danny289 Member
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    you are right :thumbup:
     
  5. zuma35

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    I double checked in my Chemistry book. I'm quoting from Brown, Lemay, "The rate constant is affected by temperature and by the presence of a catalyst."

    Also, Destroyer question 88 explicitly states that a catalyst increases the rate constant.
     
  6. Sublimation

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    Zuma is correct. It only makes logical sense. A catalyst is known to speed up a reaction. The rate constant is a measure of how quickly products are formed. Therefore it will directly afffect the rate constant. However, when it comes to the Keq thats a different story. Think of it this way. Rate constant is a measure of how fast we get to equilibrium and the equalibirum constant is just a measure of the product to reactanct ratio of a reaction. if catalysts changed equilibrium constants then we all will be in big trouble.
     
  7. sciencegod

    sciencegod Super Member
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    guys what about pressure
     
  8. Danny289

    Danny289 Member
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    yes the catalyst speed up the reaction, no doubt about that. But the point is: it is going to speed up the both directions.
     
    #7 Danny289, Dec 24, 2008
    Last edited: Dec 24, 2008
  9. Sublimation

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    Im sorry, but i dont understand what u mean by that. A catalyst will only speed up a reaction in one direction. It wont speed up production of reactants. The whole point of a catalyst is to speed up a reaction to completion in the direction of the eq.
     
  10. Danny289

    Danny289 Member
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    G chemistry long time ago but check it out. :)
    http://en.wikipedia.org/wiki/Catalyst
     
  11. Sublimation

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    "Catalysts do not change the favorableness of a reaction: they have no effect on the chemical equilibrium of a reaction because the rate of both the forward and the reverse reaction are both affected" This doesnt mean it speeds up in both directions. It means as it may speed up int he forward direction it will reduce the speed of the reverse reaction. Catalysts dont speed up the formation of product and reactants. It only speeds up the rate of one of the two. Yes it affects both, however, it does not speed the production of both.
     
  12. dentrilla

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    I always thought catalysts lowered the activation energy for reactions... this would cause both the forward and reverse reactions to require less energy and proceed faster..? Please correct me if I'm completely off track, this all came off the top of my head.
     
  13. Sublimation

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    It will increase the rate to drive the reaction to equilibrium. It wont cause it to increase in both directions.
     

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