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Thread: Solubility/Precipitating

  1. #1 Solubility/Precipitating 
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    Hello fellow chemists, I have a few question I would really appreciate it if I can get some expert opinions and answers about them.

    If a bunch of ions, lets say 4 of them are in a beaker, Na+, Cu2+, Ba2+, Pb2+, and I want to separate one from another by selectively precipitating each. I know I'm suppose to add an negative ion and then filter it but what ion am I going to add in? And one of them will remain soluble in the solution after I do so.

    Also I have another uestion regarding precipitate.
    Lets say LiCl and Na3PO4 were mixed and a precipitate formed. How is this possible? LiPO4 is soluble and NaCl is also soluble.


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  3. #2 Re: Solubility/Precipitating 
    Reptile Dysfunction drowsy turtle's Avatar
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    Quote Originally Posted by Lightz
    Lets say LiCl and Na3PO4 were mixed and a precipitate formed. How is this possible? LiPO4 is soluble and NaCl is also soluble.
    A solution is basically free ions floating about in solution. Random interactions between ions might result in lattices forming, but the solvent generally breaks them up again if the compound is soluble.

    When two solutions are mixed, these random interactions between ions can form ionic lattices of compounds that are not soluble, and so we see this compound being precipitated.


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  4. #3 Re: Solubility/Precipitating 
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    Quote Originally Posted by drowsy turtle
    Quote Originally Posted by Lightz
    Lets say LiCl and Na3PO4 were mixed and a precipitate formed. How is this possible? LiPO4 is soluble and NaCl is also soluble.
    A solution is basically free ions floating about in solution. Random interactions between ions might result in lattices forming, but the solvent generally breaks them up again if the compound is soluble.

    When two solutions are mixed, these random interactions between ions can form ionic lattices of compounds that are not soluble, and so we see this compound being precipitated.
    Going by the theory that a double displacement reaction occurs? If so then the products: Li3PO4 and NaCl are both soluble according to the solubility rules.
    This of course is an exception but why? From your answer, does it mean by random chances or does it have to do with the structure of Li3PO4 or NaCl.

    I'm still confused on this concept.
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  5. #4  
    Reptile Dysfunction drowsy turtle's Avatar
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    Possibly one or more of the ions reacts with the water.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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