# solut06 - CHAPTER SIX CHEMICAL EQUILIBRIUM Characteristics...

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114 CHAPTER SIX CHEMICAL EQUILIBRIUM Characteristics of Chemical Equilibrium 10. a. The rates of the forward and reverse reactions are equal. b. There is no net change in the composition (as long as temperature is constant). 11. False. Equilibrium and rates of reaction (kinetics) are independent of each other. A reaction with a large equilibrium constant value may be a fast reaction or a slow reaction. The same is true for a reaction with a small equilibrium constant value. Kinetics is discussed in detail in Chapter 15 of the text. 12. No, equilibrium is a dynamic process. Both reactions: H 2 O + CO H 2 + CO 2 and H 2 + CO 2 H 2 O + CO are occurring, but at equal rates. Thus, 14 C atoms will be distributed between CO and CO 2 . 13. No, it doesn’t matter which direction the equilibrium position is reached. Both experiments will give the same equilibrium position since both experiments started with stoichiometric amounts of reactants or products. The Equilibrium Constant 14. The equilibrium constant is a number that tells us the relative concentrations (pressures) of reactants and products at equilibrium. An equilibrium position is a set of concentrations that satisfy the equilibrium constant expression. An infinite number of equilibrium positions can satisfy the same equilibrium constant expression. 15. For the gas phase reaction a A + b B _ c C + d D: the equilibrium constant expression is: K = ] [B ] [A ] [D ] [C b a d c

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115 and the reaction quotient has the same form: Q = ] [B ] [A ] [D ] [C b a d c The difference is that in the expression for K we use equilibrium concentrations, i.e., [A], [B], [C] and [D] are all in equilibrium with each other. Any set of concentrations can be plugged into the reaction quotient expression. Typically, we plug in initial concentrations into the Q expression then compare the value of Q to K to see how far we are from equilibrium. If Q = K, then the reaction is at equilibrium with these concentrations. If Q K, then the reaction will have to shift either to products (Q < K) or to reactants (Q > K) to reach equilibrium. 16. The units for both reactions are: molecules cm = ) cm / (molecules ) cm / (molecules ) cm / (molecules 3 3 3 3 a. K = mol molecules 10 _ 6.022 _ cm 1000 L 1 _ molecules cm 10 _ 1.26 23 3 3 -11 = 7.59 × 10 9 L/mol K P = K(RT) n , where n = moles gaseous products - moles gaseous reactants n = 1 - 2 = -1 K p = K 300. _ K mol atm L 0.08206 L/mol 10 _ 7.59 9 ÷ ø ö ç è æ = 3.08 × 10 8 atm -1 b. K = mol molecules 10 _ 6.022 _ cm 1000 L 1 _ molecules cm 10 _ 2.09 23 3 3 -12 = 1.26 × 10 9 L/mol K P = K(RT) n , n = -1; K p = K 300. _ K mol atm L 0.08206 L/mol 10 _ 1.26 9 ÷ ø ö ç è æ = 5.12 × 10 7 atm -1 c. K* = ] NO ][ HO [ ] NO HO [ 2 2 2 2 = 1.26 × 10 -11 cm 3 /molecules
CHAPTER 6 CHEMICAL EQUILIBRIUM 116 [HO 2 NO 2 ] = (1.26 × 10 -11 ) (1.65 × 10 10 ) (6.00 × 10 12 ) = 1.25 × 10 12 molecules/cm 3 17. K p = K(RT) n where n = sum of gaseous product coefficients - sum of gaseous reactant coefficients. For this reaction, n = 1 - 2 = -1.

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solut06 - CHAPTER SIX CHEMICAL EQUILIBRIUM Characteristics...

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