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Homework Help: Why Does Saturation Need Undisolved Solute?

  1. Dec 15, 2014 #1
    1. The problem statement, all variables and given/known data

    Why is the presence of undissolved solute necessary for the solution to be considered saturated?

    2. Relevant equations


    3. The attempt at a solution

    Why can't there just be a saturated solution with no "excess" solute? For example, why can't there be a point od saturation where one more molecule would cause two molecules to bond and form the smallest "crystal" possible?

    Or am I just being too specific?
  2. jcsd
  3. Dec 16, 2014 #2


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    Gold Member

    What's the meaning of a solution being saturated? It means you can't solve any more stuff into it. But how can you understand you can't do that?
    Simple, you solve and solve and solve until no more can be solved. So the excess is only for us to understand when the saturation occurs, otherwise how can you tell you can solve any more stuff or not at any time?
  4. Dec 16, 2014 #3


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    Staff: Mentor

    I don't think it is a necessary condition.

    Technically if you take a solution that was in the equilibrium with the solid, and filter the solid out, you are left with a saturated solution that doesn't contain undissolved solute.

    This is tricky, as a slight change in temperature can make the solution unsaturated, so the presence of the solid definitely helps to make sure solution is saturated.
  5. Dec 16, 2014 #4
    Thanks guys!
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