Crystals of high ionic charge are less soluble. why?

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Discussion Overview

The discussion revolves around the solubility of crystals with high ionic charges, specifically exploring the relationship between hydration energy and lattice energy. Participants examine the factors that influence solubility, including the effects of ionic charge on these energies.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that higher ionic charges lead to greater lattice energy, which in turn results in lower solubility due to the condition that hydration energy must be less than lattice energy for solubility to occur.
  • Another participant challenges the reasoning regarding hydration energy, noting that it becomes more negative with increasing charge, which may stabilize the solution.
  • A point is made that lattice energy increases with the product of the individual charges of the ions, while the interaction energy with the hydration sphere increases more linearly, suggesting a complex relationship between these energies.
  • It is mentioned that ions with higher charges have less hydration entropy compared to singly charged ions, which may also affect solubility.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between hydration energy and lattice energy, with no consensus reached on the implications for solubility. The discussion remains unresolved regarding the correctness of the initial reasoning presented.

Contextual Notes

Participants note the need to closely examine the relative sizes of lattice energy and solvation energy, indicating that the discussion is contingent on these comparisons. Additionally, there are references to the importance of hydration entropy, which may not have been fully explored.

gracy
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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?
 
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Simon Bridge said:
Well done:
Thanks for boosting me.It really means a lot to me.
 
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.
 
gracy said:
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.
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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