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can oil disolve in water in time?
- frank (age cuellar)
I'm glad you asked this question, which gets at the distinction between the rates of processes and the equilibrium condition they're heading toward. In this case, the failure of oil to dissolve much in water is not just a result of the process being very slow. Assuming we're talking about some ordinary oil here, no matter how long you wait the concentration of oil in the water will remain very low.
It's not quite zero, however, for a very general chemical reason. The first few molecules to go into solution have an enormous entropy, growing without limit as the concentration is lowered. The equilibrium concentration of any solute is never zero, although it can be very low. So if you were to keep flowing new fresh water underneath the oil, the oil would be gradually washed away. As long as the oil and water just sit in the same pot, they mostly remain separate.
(published on 05/24/11)
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