This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: 1 Lecture 29 How Far? Gibbs Free Energy Key Idea: The amount of product depends on the magnitude and sign of the enthalpy and entropy changes. G o Temp G o Temp G o Temp G o Temp From Wednesday: G o = H o T S o H o S o + H o S o + H o S o + + H o S o Types of Problems to Solve in Chem 1A 1. Calculate the standard Gibbs free energy change ( G o ) at 298.15 K for a reaction in two different ways: (a) from the Gibbs free energies of formation ( G o f ), and (b) from H o rxn and S o rxn . 2. From this information, determine if a reaction is product-favored or reactant-favored at the standard temperature (298.15K). For a reaction that is reactant-favored, calculate the temperature above or below which the reaction becomes product-favored. 2 Mg (s) + CO 2 (g) 2 MgO (s) + C (graphite, s) Mg (s) CO 2 (g) MgO (s) C (graphite,s) H o f S o G o f-393.5-601.7 32.68 213.74 26.94 5.74-394.4-569.43 in kJ/mol in J/mol K in kJ/mol N 2 O 4 4 (g) (g) 2 NO NO 2 (g) g) Predict H o : Predict S o : 51.31 240.06 33.18 NO 2 (g) 97.89 304.29 9.16 N 2 O 4 (g) G f S H f in kJ/mol in J/mol K in kJ/mol N 2 O 4 4 (g) (g) 2 NO NO 2 (g) g) G o = H o T S o = +57,200 J 298.15 K (+175.83 J/K) = +57,200 J 52,424 J G o Temp H o S o + + Recall Le Chateliers Principle!...
View Full Document
- Fall '08