12-12-08[lecture24]jr

12-12-08[lecture24]jr - Look at which factor is determining...

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Chem 116 Lecture 24 Notes (JR) Gibbs Free Energy - Second law of thermodynamics: Entropy must always increase (the total of the system and surroundings must increase) Δ G = Δ H - T Δ S - The answer to Δ G determines the spontaneity of a reaction. If the answer is negative, then the reaction is spontaneous. If the answer is positive, then the reaction is not spontaneous. The number of Δ G will depend on the enthalpy change and the entropy change times the absolute temperature (remember to convert to Kelvin). Review Session: Monday 1PM (Room is W-1-006)
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Unformatted text preview: Look at which factor is determining the sign of G (either enthalpy or entropy change). - H 2 O(l) H 2 O(g) is a physical change because it is the same chemical but in a different state. - It is endothermic since you must put energy into it (goes from a low energy state to a higher energy state). - The gas state is in more disorder than the liquid state, so for this change the S is positive What G means: - Positive G : not spontaneous - Zero G : at equilibrium - Negative G : spontaneous...
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