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AP Chemistry Unit 9 - Equilibrium

AP Chemistry Unit 9 - Equilibrium. Lesson 6 – Gibbs’ Free Energy and Equilibrium Book Section: 19.7. Gibb’s Free Energy and Equilibrium. Remembering Gibbs’ Free Energy concepts: If Δ G < 0, the forward reaction is spontaneous. If Δ G > 0, the reverse reaction is spontaneous.

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AP Chemistry Unit 9 - Equilibrium

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  1. AP ChemistryUnit 9 - Equilibrium Lesson 6 – Gibbs’ Free Energy and Equilibrium Book Section: 19.7

  2. Gibb’s Free Energy and Equilibrium • Remembering Gibbs’ Free Energy concepts: • If ΔG < 0, the forward reaction is spontaneous. • If ΔG > 0, the reverse reaction is spontaneous. • If ΔG = 0, the reaction is in equilibrium.

  3. Reaction Conditions and Spontaneity • ΔG for a reaction is dependent on both temperature and concentrations (because a reaction could start at non-equilibrium conditions). • The relationship between ΔG (at any condition) and ΔGº (standard conditions) is: • ΔG = ΔGº + RT ln(Q). • R = ideal gas constant • T = temperature in Kelvin • Q = reaction quotient • Because R is in J/mol-K, ΔG must be in J or J/mol.

  4. Sample Exercise N2(g) + 3 H2(g)  2 NH3 (g) ΔGº = -33.0 kJ Calculate ΔG at 298 K for a reaction mixture that consists of 1.0 atm N2, 3.0 atm H2, and 0.50 atm NH3.

  5. ΔG at Equilibrium • We can rearrange this equation at equilibrium: • ΔG = ΔGº + RT ln(Q). • At equilibrium, ΔG = 0, and Q is equal to the equlibrium constant, K • 0 = ΔGº + RT ln(K). • ΔGº = —RT ln(K).

  6. Sample Exercise, Part II N2(g) + 3 H2(g)  2 NH3 (g) ΔGº = -33.0 kJ Calculate K for this reaction at 25 ºC.

  7. HW: 19.74, 19.76, 19.78, 19.80 • Next week: • Tuesday: Begin Unit 10: Acids & Bases: Arrhenius Acids and Bases (16.1) • Wednesday: Bronsted-Lowry Acids and Bases (16.2) • Thursday: Equilibrium Exam • Friday: Kw (16.3-16.4), Problem Set 8 Due

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