Inverse Solubility of Solid Solutes

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Discussion Overview

The discussion revolves around the phenomenon of inverse solubility of certain solid solutes, particularly focusing on why their solubility decreases with increasing temperature. Participants explore the thermodynamic principles involved, including exothermic and endothermic processes, and reference Le Chatelier's principle in their reasoning.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Misha questions why the solubility of some solids decreases with heat, suggesting that the exothermic nature of the dissolution process might be a factor.
  • Some participants propose that while dissolution can be accelerated by increased temperature, it does not necessarily lead to greater solubility, referencing Le Chatelier's principle.
  • Another participant highlights the importance of examining the temperature dependence of the equilibrium constant for the dissolution process.
  • Misha reiterates their initial question and introduces a comparison between exothermic and endothermic processes, suggesting that increasing temperature could either reduce or increase solubility depending on the nature of the reaction.
  • There is a mention of the behavior of gases in relation to temperature and solubility, noting that gases typically have reduced solubility in warmer conditions.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between temperature and solubility, with no consensus reached on the mechanisms at play or the implications of Le Chatelier's principle in this context.

Contextual Notes

Participants reference specific thermodynamic principles and the behavior of gases, but the discussion does not resolve the complexities surrounding the conditions under which solubility changes with temperature.

Misha Kuznetsov
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Why is the solubility of some solids lower when the solution is heated? I read that it is because the process is exothermic (heat from breakdown is greater than the heat needed for breakdown). But why would having extra heat from outside sources inhibit the dissolving process, wouldn't it only help it?

My source: http://www.chem.fsu.edu/chemlab/chm1046course/solubility.html

-Misha
 
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Dissolution can be speed up by the increasing temperature, but the solubility doesn't have to grow. Think in terms of Le Chatelier's principle.
 
The other thing you'll want to examine is the temperature dependence of the equilibrium constant for the solution process.
 
Misha Kuznetsov said:
Why is the solubility of some solids lower when the solution is heated? I read that it is because the process is exothermic (heat from breakdown is greater than the heat needed for breakdown). But why would having extra heat from outside sources inhibit the dissolving process, wouldn't it only help it?

My source: http://www.chem.fsu.edu/chemlab/chm1046course/solubility.html

-Misha

As Borek noted think about this in terms of Le Chatelier:

solid + H2O --> solute + heat (exothermic) ---> Increasing T will reduce solubility

solid + H2O + heat ---> solute (endothermic) --> Increasing heat will increase solubility

Interestingly, gases typically have reduced solubility in water with increasing temperature -- one reason why warm soda tastes bad...
 

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