CHAPT15B F10

CHAPT15B F10 - Chapter 15 CHEMICAL EQUILIBRIUM CHEMICAL EQUILIBRIUM a state of dynamic balance in which the rate of formation of the products of a

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Chapter 15 CHEMICAL EQUILIBRIUM CHEMICAL EQUILIBRIUM  - a state of dynamic balance in which the rate of formation of the  products of a reaction from the reactants equals the rate of formation of the reactants from  products; at equilibrium the concentrations of the reactants and products remain constant. KINETICS ARGUMENT FOR EQUILIBRIUM  Consider the reaction of        Double arrows indicate equilibrium and the “steady state” Forward reaction A -----> B rate = k f [A]  Reverse reaction B -----> A  rate = k r [B] Rate of the forward reaction is equal to the rate of the reverse reaction k f [A] = k r [B]     then k f /k r  = [B]/[A]  K c  = k f /k r   and K c  also equals [B]/[A]   K c  = [B]/[A]    K c  is the equilibrium constant (See Figure 15.1 and 15.2 on page 629 for a real life example) THE LAW OF MASS ACTION  - this law expresses the relative concentrations of reactants and  products at equilibrium in terms of a quantity called the equilibrium constant, K.                a A  +   b B     c C  +   d D A, B, C, and D  are the chemical species in the reaction. a, b, c,  and  are their coefficients in the balanced chemical equation. The equilibrium condition is expressed by  K c      =   [C]        [D]     d                    K p     =   P c c        P     D d      .                   [A] a   [B] b                                     P A a     P b                                        Board discussion  of the equilibrium expression. Example problem 1 BOARD DISCUSSION OF K AND THE EQUILIBRIUM EXPRESSION 1. Review: K is  a ratio; K is a constant; K is defined by the equilibrium expression for a given  system at a given temperature Joan Hilderbrandt, Chem. 12           1
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2. The units of K c  and K p  are determined by the powers of the concentration terms. K c  and K p  are  often unit less  3. For a reaction at equilibrium at a given temperature, there are many equilibrium positions but 
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This note was uploaded on 03/04/2012 for the course PUBH 2113 taught by Professor Edberg during the Fall '11 term at GWU.

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CHAPT15B F10 - Chapter 15 CHEMICAL EQUILIBRIUM CHEMICAL EQUILIBRIUM a state of dynamic balance in which the rate of formation of the products of a

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