Zumdahl+Chapter+6+Lecture+Notes

Zumdahl+Chapter+6+Lecture+Notes - Chapter 6 Chemical...

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10/30/07 Zumdahl Chapter 2 1 Chapter 6 Chemical Equilibrium 6.1 The Equilibrium Condition 6.2 The Equilibrium Constant 6.3 Equilibrium Expressions Involving Pressures 6.4 The Concept of Activity 6.5 Heterogeneous Equilibria 6.6 Applications of the Equilibrium Constant 6.7 Solving Equilibrium Problems 6.8 Le Chatelier's Principle 6.9 Equilibria Involving Real Gases
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Properties of Equilibrium State ! Equilibrium systems: – Dynamic: forward and reverse processes – Display no net change in time – Can be approached from either direction, reactants or products – Reached through spontaneous processes Pink to blue Co(H 2 O) 6 2+ + 4 Cl - ! Co(Cl) 4 2- + 6 H 2 O Blue to pink Co(Cl) 4 2- + 6 H 2 O ! Co(H 2 O) 6 2+ + 4 Cl - 10 M HCl H 2 O 10 M HCL H 2 O
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10/30/07 Zumdahl Chapter 2 3 Chemical Reactions and Equilibrium The equilibrium condition for every reaction can be described in a single equation in which a number, the equilibrium constant (K) of the reaction, equals an equilibrium expression , a function of properties of the reactants and products. H 2 O( l ) ! H 2 O( g ) @ 25 o C Temperature ( o C) Vapor Pressure (atm) 15.0 0.01683 17.0 0.01912 19.0 0.02168 21.0 0.02454 23.0 0.02772 25.0 0.03126 30.0 0.04187 50.0 0.1217 H 2 O( l ) ! H 2 O( g ) @ 30 o C K = 0.03126 K = 0.04187
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10/30/07 Zumdahl Chapter 2 4 H 2 O (g) + CO (g) ! H 2 (g) + CO 2 (g) CO O H CO H p P P P P K 2 2 2 =
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10/30/07 Zumdahl Chapter 2 5 Chemical Reactions and Equilibrium As the equilibrium state is approached, the forward and backward rates of reaction approach equality. At equilibrium the rates are equal, and no further net change occurs in the partial pressures of reactants or products. 1. They display no macroscopic evidence of change. 2. They are reached through spontaneous processes. 3. They show a dynamic balance of forward and backward processes. 4. They are the same regardless of the direction from which they are approached. Four fundamental characteristics of equilibrium states in isolated systems: dD cC bB aA + ! ! ! " ! ! ! # ! + reverse forward
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10/30/07 Zumdahl Chapter 2 6 The Form of Equilibrium Expressions In a chemical reaction in which a moles of species A and b moles of species B react to form c moles of species C and d moles of species D, the partial pressures at equilibrium are related through provided that all species are present as low-pressure gases. dD cC bB aA + ! ! ! " ! ! ! # ! + reverse forward
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10/30/07 Zumdahl Chapter 2 7 Law of Mass Action Partial pressures and concentrations of products appear in the numerator and those of the reactants in the denominator. Each is raised to a power equal to its coefficient in the balanced chemical equation. aA + bB ! cC + dD if gases P C ( ) c P D ( ) d P A ( ) a P B ( ) b = K if concentrations C [ ] c D [ ] d A [ ] a B [ ] b = K
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10/30/07 Zumdahl Chapter 2 8 Write equilibrium expressions for the reactions defined by the following equations: 3 H 2 ( g ) + SO 2 ( g ) H 2 S( g ) + 2 H 2 O( g ) 2 C 2 F 5 Cl( g ) + 4 O 2 ( g ) Cl 2 ( g ) + 4 CO 2 ( g ) + 5 F 2 ( g )
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10/30/07 Zumdahl Chapter 2 9 Heterogeneous Equilibrium Solids Liquids Dissolved species H 2 O( l ) ! H 2 O( g ) = K CaCO 3 ( s ) ! CaO( s ) + CO 2 ( g ) = K I 2 ( s ) ! I 2 ( aq ) = K K is independent of the amounts of CaCO 3 or CaO
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