20 FreeEnergy Landscape

20 FreeEnergy Landscape - Entropy and Spontaneity Does an...

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CHEM 112 LRSVDS Thermo part 2 1 Does an Increase in S mean the reaction is spontaneous? ! S spontaneous? H 2 O(l) (25°) # H 2 O(g) CaCO 3 (s) # CaO(s) + CO 2 (g) N 2 (g) + 3H 2 (g) # 2NH 3 (g) N 2 (g) + O 2 (g) # 2NO(g) Mg(s) + Cl 2 (g) # MgCl 2 (s) Ag + (aq) + Cl - (aq) # AgCl(s) Na + (aq) + CH 3 COO - (aq) # CH 3 COONa(s) Entropy and Spontaneity CHEM 112 LRSVDS Thermo part 2 2 CRITERIA FOR SPONTANEITY ! H Exothermic reactions ( ! H <0) are usually spontaneous. ! S Spontaneous if ! S system + ! S surroundings > 0 We need a new state function that can predict spontaneity. This is called the Gibbs Free Energy : ! G = ! H ! T ! S T is absolute temperature (units of K). ! G refers to a reaction at constant T and P. ! G < 0 Spontaneous ! G > 0 Not spontaneous ! G = 0 System at equilibrium.
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CHEM 112 LRSVDS Thermo part 2 3 Gibb’s Free Energy CHEM 112 LRSVDS Thermo part 2 4 STANDARD FREE ENERGY OF FORMATION ! G f ° Free energy change in forming one mole of a compound from its elements each in their
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20 FreeEnergy Landscape - Entropy and Spontaneity Does an...

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