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Crystals of high ionic charge are less soluble. why?

  1. Apr 19, 2015 #1
    Crystals of high ionic charge are less soluble. why?As we know,when hydration energy is less than lattice energy the ions are not soluble.
    So,crystals of high ionic charges have less hydration energy right?And it does make sense to me as higher the charge ,greater the lattice energy because lattice energy is proportional to charge.And higher the charge ,easier to form bond with water so greater is extent of solvation so less energy required for hydration,hence less hydration energy.
    Thus,overall the criteria to be less soluble is
    fulfilled i.e lattice energy is greater than hydration energy.

    Is my reasoning correct?
     
    Last edited: Apr 19, 2015
  2. jcsd
  3. Apr 19, 2015 #2

    Simon Bridge

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  4. Apr 19, 2015 #3
    Thanks for boosting me.It really means a lot to me.
     
  5. Apr 19, 2015 #4

    Simon Bridge

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    No worries - It's good to see people using their wits :)
    The link I gave you makes a more complete case though... do read: it should deepen your understanding.

    Aside: when typing, always put a space character, " ", after sentence punctuation characters - that's ", ; : . ? !" you get the idea.
    Compare what I've just written with your post #1 to see what I mean... I put a space after commas and periods etc. It makes your typing easier to read, and makes your output look more "pro", but is otherwise no biggie.
     
  6. Apr 20, 2015 #5

    DrDu

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    Er, no, the last conclusion is not correct, or only formally so, as hydration energy is negative, and will become more negative with increasing charge. However, you have to note that this will tend to stabilize the solution. So the lattice energy and the solvation energy are really competing, and you have to discuss more closely their relative size.
    One point is that in lattices made up from highly charged species, the lattice energy will go up like the product of the individual charge of the ions (e.g. 2x2 for MgO or 3x2 for Al2O3) while the interaction energy between an ion and the hydration sphere will be more linear in charge, i.e. does not increase as fast. Ions of higher charge n will also have less hydration entropy as compared to n singly charged ions.
     
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