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Ksp

Discussion in 'DAT Discussions' started by peyman2002, Dec 9, 2008.

  1. peyman2002

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    I need for somebody to explain this:
    we have Na2(So4) saturated solution and we add base according to the answer the following occurs:

    Increasing the solution’s basicity will disrupt the equilibrium between sulfate and its conjugate acid leading to an increase in sulfate ion concentration: HSO4- + OH- -> SO42- + H2O. An increase in sulfate ion concentration will cause precipitation of sodium sulfate via the common ion effect.

    ok. Na2So4 is soluble and if we add OH should NaOH form which would result in disolving more of Na2So4?
     
  2. Danny289

    Danny289 Member
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    base is not in saturated in our soluion, we won't have reverse for NaOH.
     
  3. peyman2002

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    danny ghorboonet, bazam nageraftam!
    could u explain more plz?
     
  4. Danny289

    Danny289 Member
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    Okay Paymanjan lets try together we have these two equations
    1) Na2SO4 <===>2 Na+ +SO42-
    2) SO4-2 + H20 <===> HSO4- + OH-

    Now adding base, means adding OH-,
    In your second equation you are increasing OH- then your equilibrium will shifts to the left that means more SO4-2.
    Just remember we can not write anything like Na+ +H2O <===> NaOH + H+
    Even you can approach another way but maybe it is a little more conceptual. Lets try this:
    1)Na2SO4 + 2H20 <===>2( Na+ + OH-) +(SO42- + 2H+)
    2)H20<====> OH- + H+
    Now you are adding OH- in second equation it will shift to the left. That means you have more water in your solution therefore you have more water in equation “1”then it will shift to the right that means more SO4-2. ( adding OH- , is not going to affect your first equation because Na2SO4 has much much bigger Keq compare to H2O)
    omidvaram gerfteh bashi aziz, soale nesbatan sakhti bood. :)
     
  5. peyman2002

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    Thanks danny ur the man.
     

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