Quote:
Originally Posted by WebSlave
So that *free* oxygen that is not bound to hydrogen to form water is dissolved into what, exactly? What is it bound to that keeps it from just rising to the top of all the water and then exiting into the atmosphere?
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Oxygen and other gases dissolved in water don't leave spontaneously when they are in balance with the amount of those same gases in the atmosphere. You can increase the amount of a gas in water by increasing the amount in the atmosphere, and vice versa.
This is why the rise in atmospheric CO2 concentrations is causing an increase in CO2 dissolved in the ocean, and is messing up corals and other calcifying organisms that are inhibited by the excess of CO2.
Also, water that is supersaturated with a gas (like Pepsi, with CO2) releases some of that gas as soon as atmospheric air hits the top of the soda when you open the can (it releases the CO2 until it is in balance with the level of CO2 in the atmosphere). Similarly, you can supersaturate a liquid with a gas simply by putting the liquid in a container and putting the gas on top of it and pressurizing the thing -- I have a cap that attaches to a bottle and hooks to a CO2 cylinder to carbonate individual bottles of homebrew (really strong beer is a bear to carbonate naturally, since the yeast dies at a certain alcohol content).
The first part of your question -- about just what 'dissolved' means in the case of oxygen -- I guess I don't understand myself. Here's an answer by someone who claims to be a Biochem Prof Emeritus (
https://www.quora.com/How-does-oxyge...olar?share=1):
Q: "How does oxygen dissolve in water despite being non-polar?"
A:"Non polar molecules do fit into cavities in water, or rather, water forms cavities to accommodate them even though the free energy for doing so is unfavorable. Once in the cavity, non polar molecules do have a force of attraction with water, namely, van der Waals - London dispersion interactions. All molecules are attracted to each other via these forces, even in the absence of other forces such as hydrogen bonds and electrostatic interactions."
There are entries in Wikipedia for Van der Waals forces and London dispersion interactions, but I didn't get very far reading them (though there is a fun little historical aside in the Van der Waals entry about gecko toes).
I'm sort of surprised a real career chemist hasn't jumped in here to correct my probably sloppy explanations (no offense to Ed, who certainly has more chemistry background than I do).