10-19 - Effect of H and S G= H-T S An exothermic rxn that...

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(-) G = H - T S (-) (+) Effect of  H and  S An exothermic rxn that spreads energy.  Yeah!  It will always be spontaneous ( G <0). Section 9.7 2Na(s) + 2H O(l)   2H (g) + 2NaOH 0 mol gas   2 mol gas Energy Dispersed   S > 0 Gives off heat  H < 0 A fool could get this reaction to work. - (-)
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(+) G = H - T S (+) (-) An endothermic rxn that concentrates energy. This will rxn will never, ever  happen spontaneously ( G >0) Section 9.7 2H O (l) + O (g)   2H O  (aq) 1 mol gas   0 mol gas Energy concentrated   S < 0 Requires heat  H > 0 Effect of  H and  S Laugh at the fool that tries to get this to work spontaneously. - (+)
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G = H - T S (-) (-) An exothermic rxn that concentrates energy. As long is the temperature is low, (T S smaller than  H) it will happen spontaneously. Section 9.7 H O(l)   H O(s) liquid   solid Energy concentrates   S  < 0 Gives off heat  H  < 0 S L G S L G H Effect of  H and  S - (+) News flash:  Stuff freezes when it’s cold.
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G = H - T S (+) (+) An endothermic rxn that spreads energy. As long is the temperature is high (T S larger than  H) it will happen Section 9.7 H O(l)   H O(g) 0 mol gas   1 mol gas Energy Dispersed   S > 0 Requires heat  H > 0 S L G S L G H Effect of  H and  S - (-) News flash:  Stuff evaporates when it’s hot.
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Reaction Spontaneity Summary H S Spontaneous ( G < 0) - + always + - never + + at high T, when |T S| > | H| - - at low T, when | H| > |T S| Section 9.7 Summary G = H - T S At low temp,  G is the same sign as  H At high temp,  G is the opposite sign of  S, unless  S~0, in which case,  G is the same sign as  H
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 Free Energy ( G) temperature G < 0 rxn spontaneous G > 0 rxn non-spon H>0 H>0,  S>0 rxn works at hi temp + + slope = -T S ( S > 0) H<0 H<0,  S>0 rxn works every time - + slope = -T S ( S < 0) H<0,  S<0 rxn works at lo temp - - H>0,  S<0 rxn never works + - Section 9.8 Free Energy, Enthalpy and Entropy
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Can we predict if a process will occur on its own?
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