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03 Notes - Quantitative Gibbs

# 03 Notes - Quantitative Gibbs - Aim How is thermodynamic...

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Aim: How is thermodynamic data used to calculate G? QQ: When can an endothermic reaction occur spontaneously? Do Now: What pieces of information do you need to calculate G? Quick Review: Gibbs Free Energy o If G is ( ) the reaction is spontaneous o If G is (+) the reaction is non-spontaneous Quantitative Thermodynamics Consider the decomposition of H 2 O 2 (hydrogen peroxide) at 298 K and 1 atm pressure according to: 2 H 2 O 2 (l) 2 H 2 O(l) + O 2 (g) Substance H (kJ/mol) S (J/K mol) H 2 O 2 (l) -187.6 109.5 H 2 O (l) -285.8 69.4 O 2 (g) 0 205 Find G for the reaction. Calculate H and S for the reaction H = -196.4 kJ S = 124.8 J/K This reaction will be spontaneous! Use Gibb’s Free Energy equation to find G… G = H T S G = -196.4 298(0.1248) *don’t forget to convert! G = -196.4 37.2 G = -233.6 kJ reaction is spontaneous G can also be calculated the same way as H and S G rxn = nG products nG reactants Consider the decomposition of H

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