AP Chemistry Concepts THERMODYNAMICS contained in Big Idea 5 – – 1. rxn = 0Products - Reactants Hf Hf0 ∆H0 ∑ ∆ ∑∆ = Bond Energy Reactants - Bond energy Products ∑ ∑ - exothermic + endothermic ∆Hrxn ∆Hrxn 2. rxn = Products - Reactants Sf0 Sf0 ∆S0 ∑ ∑ - ordered + disordered ∆S0rxn ∆S0rxn 3. rxn = - 0rxn T ∆G0 ∆H0rxn ∆S - thermodynamically favored ∆G0rxn + thermodynamically unfavored ∆G0rxn 4. = - ln = free energy and equilibrium ∆G0rxn RT Q Q Keq 5. rxn = - free energy and electrochemistry nF E0 ∆G0 = 96,500 coulombs / mole electrons F Faraday’s constant 6. Phase diagrams 7. rxn = = ( ) ( ) q m c ∆H ∆T Free Response Questions 1998 # 3 C6H5OH(s) + 7 O2(g) 6 CO2(g) + 3H2O(l) → When a 2.000-gram sample of pure phenol, C6H5OH(s), is completely burned according to the equation above, 64.98 kilojoules of heat is released. Use the information in the table below to answer the questions that follow. Standard Heat of Formation, Substance Absolute Entropy, at 25°C (J/mol-K) S°, at 25°C (kJ/mol) ΔH°f, C(graphite) 0.00 5.69
AP Chemistry Concepts – THERMODYNAMICS – contained in Big Idea 5 1. ∆H0 rxn = ∑ ∆ Hf 0Products - ∑∆ Hf0 Reactants = ∑ Bond Energy Reactants - ∑ Bond energy Products ∆Hrxn - exothermic ∆Hrxn + endothermic 2. ∆S0 rxn = ∑ Sf0 Products - ∑ Sf0 Reactants ∆S0rxn - ordered ∆S0rxn + disordered 3. ∆G0 rxn = ∆H0rxn - T ∆S 0rxn ∆G0rxn - thermodynamically favored ∆G0rxn + thermodynamically unfavored 4. ∆G0rxn = - RT ln Q Q = Keq free energy and equilibrium 5. ∆G0 rxn = - nF E0 free energy and electrochemistry F = 96,500 coulombs / mole electrons Faraday’s constant 6. Phase diagrams 7. ∆H rxn = q = m ( c ) ( ∆T ) Free Response Questions 1998 # 3 C6H5OH(s) + 7 O2(g) → 6 CO2(g) + 3H2O(l) When a 2.000-gram sample of pure phenol, C6H5OH(s), is completely burned according to the equation above, 64.98 kilojoules of heat is released. Use the information in the table below to answer the questions that follow. Substance Standard Heat of Formation, ΔH°f, at 25°C (kJ/mol) Absolute Entropy, S°, at 25°C (J/mol-K) C(graphite) 0.00 5.69