Why do salts dissolve better in warm water, but not gases?

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Offline thedoc

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Chris, here's a question of the week for you.

I use lots of soda water with a home charging unit, and the first thing I learned is to chill the water before injecting the CO2. Otherwise the gas is poorly absorbed, and the water doesn't have much fizz.
On the other hand, in chemistry I learned that most compounds (usually salts of various types) dissolve much better in warm rather than cold water. Why does it work one way with salts and the opposite way with gasses?
John Gamel

Asked by John Gamel

                                        Visit the webpage for the podcast in which this question is answered.

[chapter podcast=3948 track=12.04.29/Naked_Scientists_Show_12.04.29_10067.mp3]  ...or Listen to the Answer[/chapter] or [download as MP3]

« Last Edit: 02/05/2012 13:45:17 by _system »


Offline Sprool

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cooling the gas reduces volatility so more goes into the liquid, but salts dissolve easier in warm water as there is more energy to ionise the salt, separate the ionic bonds and thus make it dissolve.


Offline CliffordK

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I think of gases as as partial pressures.... 
The higher temperature, the higher partial pressure...  and thus the more it is driven out of solution.

Salts, of course, do not easily vaporize at lower temperatures.