Reduction in gas concentration of water with solutes

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Discussion Overview

The discussion revolves around the phenomenon of gas concentration reduction in water when solutes, particularly polar solutes like salt and phenol, are added. Participants explore the mechanisms behind this effect, including the role of solvation and the structuring of water molecules.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that adding salt to water increases its polarity and may lead to the "driving" out of oxygen from solution, speculating on electrostatic repulsion as a possible mechanism.
  • Another participant notes that the origin of the salting out phenomenon is still debated, indicating that certain ionic solutes may enhance the structuring of water, thereby reducing the solubility of hydrophobic solutes like O2.
  • There is a question raised about whether phenol, which can dissolve in water due to hydrogen bonding but is mostly non-polar, would also cause a degassing effect similar to that of salt.
  • One participant expresses uncertainty about whether phenol is a more "structure-making" solute compared to NaCl, suggesting that larger solutes are generally less likely to create such structures.
  • A request for further explanation on the "structuring" aspect of solvation is made, indicating a desire for deeper understanding of the topic.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the mechanisms behind the reduction in gas concentration or the comparative effects of different solutes. Multiple competing views and uncertainties remain regarding the role of solvation and structuring in this context.

Contextual Notes

The discussion highlights limitations in current understanding, particularly regarding the definitions and implications of "structuring" in relation to solvation and gas solubility. There are also unresolved questions about the specific effects of different solutes on gas concentration in water.

rwooduk
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When salt (polar) is added to water (polar) it makes the water more polar and causes the oxygen (non-polar) to be "driven" from solution. So I'm assuming this is an electrostatic repulsion(?).

Aside from salt what other solutes would cause this to happen? Would a solute have to have very polar molecules? In particular would phenol, which can dissolve in water due to hydrogen bonding, but is mostly non-polar cause this 'degassing' effect?

Any feedback on the above would be very much appreciated.
 
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The origin of salting out phenomena is still a subject of active debate and study, so I don't think there is any definitive answer to your question, although theories, both serious and pop science, abound. The bottom line appears, so far, to be that certain ionic solutes cause an enhanced "structuring" of the water and the solubility of hydrophobic solutes (like O2) may be decreased for no more complicated reason than that the effective volume of water in which they can dissolve is reduced. What's important to your question, therefore, is whether phenol is a more "structure-making" solute than, say, NaCl. It probably isn't: generally larger solutes appear to be less likely to be "structure making."
 
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Christopher Grayce said:
The origin of salting out phenomena is still a subject of active debate and study, so I don't think there is any definitive answer to your question, although theories, both serious and pop science, abound. The bottom line appears, so far, to be that certain ionic solutes cause an enhanced "structuring" of the water and the solubility of hydrophobic solutes (like O2) may be decreased for no more complicated reason than that the effective volume of water in which they can dissolve is reduced. What's important to your question, therefore, is whether phenol is a more "structure-making" solute than, say, NaCl. It probably isn't: generally larger solutes appear to be less likely to be "structure making."

Many thanks for the reply that's extremely helpful. I'll see if I can find some papers on salting out, however the ones I've seen don't really talk about a reduction in gas concentration. Could you perhaps explain the "structuring" aspect a little more?
 
rwooduk said:
Could you perhaps explain the "structuring" aspect a little more?

Google solvation, solvation shell - molecules involved in solvation are no longer part of the bulk solvent..
 
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Borek said:
Google solvation, solvation shell - molecules involved in solvation are no longer part of the bulk solvent..

Excellent, will do. Thanks again.
 

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