^^Entropy^^: dispersal of matter/energy in sample of matter
changes of entropy can be seen as how dispersed the matter/energy is
entropy increases when matter is more dispersed
individual particles at increased entropies are more free to move and occupy more space
With gases:
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entropy also increases when energy is more dispersed
according to KMT, K.E among particles broadens when temperature increases
entropy increases when temperature increases
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entropy change can be calculated from absolute entropies in individual species
most substances have a nonzero value for absolute entropy unlike enthalpy
when calculating, number of moles of each substance have to be considered
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^^Find delta S with: ΔS=∑S(products)−∑S(reactants)^^
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entropy is positive if : phase changes occur as, solid to liquid to gas or if number of moles increase from reactants to products
entropy is negative if: phase changers occur as, gas to liquid to solid
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^^Gibbs free energy:^^ △G describes if a reaction is thermodynamically favorable or unfavorable
^^Thermodynamically favorable:^^ equation proceeds to equilibrium with no outside factors
reminder! just because reaction is favorable does not mean it happens quickly
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in Gibbs free energy all reactants and products are in standard states (pure substance, 1.0M, 1 atm)
^^Find delta G with: ΔG=∑G(products)−∑G(reactants)^^
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thermodynamically favorable, G=negative
thermodynamically unfavorable, G=positive
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G can be calculated from enthalpy and entropy with: ^^ΔG=ΔH-TΔS^^ * t=temperature
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processes that are favorable but do not make products at measurable rate, are under kinetic control
a catalyst (ex. enzyme) can decrease Ea and increase reaction rate, but has no effect on favorability
even if the process doesn't happen at a noticeable rate, it does not mean it's at not equilibrium
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thermodynamically favored (ΔG
at equilibrium, no net change in concentration of reactants and products occurs
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^^Find K with: K=e-GT/RT^^
Find Delta G with: ΔG° = -RTlnK *R = 8.314 J mol-1 K-1
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-when ΔG is neg, K>1, reaction favors products
when ΔG is pos, K<1, reactions favors reactants
when ΔG=0, reaction is at equilibrium
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^^Coupling:^^ when two reactions share an intermediate, they can be coupled, Hess’s law can be applied and the sum of the reactants’ ΔG values makes overall process favorable when added
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