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Posted by on Jul 13, 2011 in Physical Chemistry | 0 comments

Heat Flow and Work – Thermodynamic Coupling

The Third Law of Thermodynamics says: if two separated systems are in thermal contact with a third, then at equilibrium they all have the same temperature.

Clearly when we bring two blocks together, heat will flow between them. This is an example of coupling systems A to B and to C so eventually the three will be in equilibrium. This coupling only allows heat to flow through direct contact.

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Posted by on Jun 30, 2011 in Physical Chemistry | 1 comment

Understanding State Functions and Reversible Paths

First it is never possible to obtain a true reversible path. It is an idealized case in which at every step along the way the system (the ball) is in equilibrium with its surroundings. Clearly if something is at equilibrium there is no noticeable change. Hence one says that a reversible process happens so slowly that equilibrium is always maintained.

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Posted by on Jun 6, 2011 in Physical Chemistry | 0 comments

The Chemical Kinetics of Sobering Up

The time to reduce 4 beers to 2 is two hours. The time to go from 2 beers to 1 is one hour, and the time to go from 1 beer to the legal limit is 30 minutes. It therefore takes a whooping 3.5 hours to reach the legal limit: 4 beers take seven times longer to metabolize than 1 beer.

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