Degree of dissociation accurately defined

  1. Is the degree of dissociation the value of

    Alpha when the dissociation begins with 1 mole of the solute, or is it alpha when the solute is 1 mole at equilibrium,



    There isn't a difference since I'm talking about very weak electrolytes but I want to know the accurate answer.
     
  2. jcsd
  3. Borek

    Staff: Mentor

    Degree of dissociation is a fraction of substance that dissociated, and it doesn't depend on the amount of substance dissolved.
     

  4. It's said on Wikipedia that is the value of dissociated moles per 1 mole,

    It is meant one mole at equilibrium or when the dissociation begins with that 1 moles ?
     
  5. Borek

    Staff: Mentor

    I don't care about what wikipedia says. Degree of dissociation is a fraction of the substance that dissociated. You start with n moles, m moles dissociate, degree of dissociation is m/n.
     

  6. Ok, m/n will give the value of m when n is 1, there's no contradiction
     
  7. Borek

    Staff: Mentor

    No contradiction, but a lousy thinking. Ratio doesn't require referring to the amount of substance.
     

  8. "n moles" is the number of moles at equilibrium or the number of moles that the dissociation starts with ???
     
  9. DrDu

    DrDu 4,090
    Science Advisor

    The degree of dissociation can be defined independently of equilibrium.
    E.g., you could measure it as a function of time after bringing an undissociated substance into a solvent.
     
  10. Borek

    Staff: Mentor

    Perhaps it is time you start paying attention to what you read.
     

  11. I'm sorry, thanks a lot for you help
     
  12. I have a question about the ionic product of water

    How is Kw = [ H ] [ OH ] = 10^-14 mole/ liter derived.
     
  13. Borek

    Staff: Mentor

    It is not derived, it is determined experimentally.

    Please start new threads for new questions.
     
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