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Homework Help: Solubility question

  1. May 29, 2006 #1
    Why does the solubility of KNO3, in water, rises with increasing temperature and the solubility of Na2SO4 descreases? :approve:
    Thank you. :wink:
     
  2. jcsd
  3. May 29, 2006 #2

    Gokul43201

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    What are your thoughts ?

    We can't help you unless you help yourself. :biggrin:
     
  4. May 29, 2006 #3
    I am sorry. I usually help people who do not present their thoughts, I never remeber those rules.

    Here are my thoughts:
    1. The dissolution of a salt involves two phases. First, the separation of the ions, which is endoenergetic because involves breaking of ionic bonds and, second, the solvatation, in this case, an hydration since the solvent is water, which is exoenergetic.

    2. If the energy consumed in the first phase is greater than the energy freed in the second phase, the dissolution of the salt is globally endoenergetic. If the energy consumed in the first phase is minor than the energy freed in the second phase, the dissolution of the salt is globally exoenergetic.

    Conclusion: I think, then, that the dissolution of KNO3 is globally endoenergetic, so rises with increasing temperature, and the dissolution of Na2SO4 is globally exoenergetic so decreases with increasing temperature.

    Am I right?
     
  5. May 29, 2006 #4

    Gokul43201

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    Perfectly.

    PS : Please do not help folks that show no original effort. It is rarely helpful to the student in the long run.
     
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