State Properties

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Chu 3J
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Joined: Fri Sep 25, 2015 3:00 am

State Properties

Postby Chu 3J » Mon Jan 11, 2016 10:32 am

If enthalpy is equal to heat (at constant pressure), and enthalpy is a state function, why isn't heat (q) considered a state function as well?

William Chwa 1E
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Joined: Fri Sep 25, 2015 3:00 am

Re: State Properties

Postby William Chwa 1E » Mon Jan 11, 2016 10:59 am

Q is not considered a state function because it is path dependent. Enthalpy is determined by the internal energy, pressure, and volume, which are all state functions. Q, however, is a process state that depends on specific transitions between equilibriums.

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Re: State Properties

Postby Chem_Mod » Mon Jan 11, 2016 3:52 pm

The above discussion is excellent! A small analogy, if you set the amount of gas needed to travel on the shortest way to go from UCLA to Hollywood is Qp, then it equals to enthalpy and it will always be the same because the distance between them does not change (do not take into account gas efficiency). But if you choose another routes, the amount of gas you burn will vary accordingly. That is similar with heat and work which depend on route you take.

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