chem sf 3 - Tro Chemistry A Molecular Approach 1 Entropy...

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Unformatted text preview: Tro, Chemistry: A Molecular Approach 1 Entropy Change in State Change • when materials change state, the number of macrostates it can have changes as well – for entropy: solid < liquid < gas – because the degrees of freedom of motion increases solid liquid gas → → Tro, Chemistry: A Molecular Approach 2 Heat Flow, Entropy, and the 2 nd Law Heat must flow from water to ice in order for the entropy of the universe to increase Tro, Chemistry: A Molecular Approach 3 Temperature Dependence of ∆ S surroundings • when a system process is exothermic, it adds heat to the surroundings, increasing the entropy of the surroundings • when a system process is endothermic, it takes heat from the surroundings, decreasing the entropy of the surroundings • the amount the entropy of the surroundings changes depends on the temperature it is at originally – the higher the original temperature, the less effect addition or removal of heat has T H S system gs surroundin ∆- = ∆ Tro, Chemistry: A Molecular Approach 4 Gibbs Free Energy, ∆ G • maximum amount of energy from the system available to do work on the surroundings G = H – T ∙ S ∆ G sys = ∆ H sys – T ∆ S sys ∆ G sys = – T ∆ S universe ∆ G reaction = Σ n ∆ G prod – Σ n ∆ G react • when ∆ G < 0, there is a decrease in free energy of the system that is released into the surroundings; therefore a process will be spontaneous when ∆ G is Tro, Chemistry: A Molecular Approach 5 Gibbs Free Energy, ∆ G • process will be spontaneous when ∆ G is negative • ∆ G will be negative when – ∆ H is negative and ∆ S is positive • exothermic and more random – ∆ H is negative and large and ∆ S is negative but small • Largely exothermic and slightly less random – ∆ H is positive but small and ∆ S is positive and large • Slightly endothermic and much more random • or high temperature • ∆ G will be positive when ∆ H is + and ∆ S is − • never spontaneous at any temperature • when ∆ G = 0 the reaction is at equilibrium Example 17.3Example 17....
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This note was uploaded on 03/26/2011 for the course CHEMISTRY 2401 taught by Professor Staff during the Spring '11 term at Georgia State.

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chem sf 3 - Tro Chemistry A Molecular Approach 1 Entropy...

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