Chapter 14 notes

Chapter 14 notes - Chapter 14 Objectives(Chemical...

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Chapter 14 Objectives (Chemical Equilibrium) Spring 2084 1. Define the concepts of reversibility and dynamic equilibrium. a) Consider a hypothetical experiment in which 2.0 mol NH 3 is added to a 5.00 liter vessel at 300° C. Now take an identical 5.00 liter flask and inject 3.0 mol H 2 and 1 mol N 2 at 300° C. After a period of time elapses, both flasks have identical compositions; there are identical mixtures of N 2 , H 2 , and NH 3 in each. b) The reaction N 2(g) + 3 H 2(g) 2 NH 3(g) is reversible and a reversible reaction is said to be in dynamic equilibrium if the left to right rate (forward) equals the right to left rate (reverse). c) In principle, all chemical reactions are reversible given the proper conditions. 2. Define the Equilibrium Constant. a) The equilibrium constant defines the concentration or pressure ratios of products to reactants in a quantitative manner. b) For a A + b B c C + d D b a d c ] B [ ] a [ ] D [ ] C [ K = , where [ ] indicate molar concentrations. c) For H 2(g) + I 2(g) 2 HI (g) ] I ][ H [ ] HI [ K 2 2 2 = Example 1: Write the K = expression (Law of Mass Action) for a) CO (g) + 1/2 O 2(g) CO 2(g) b) N 2(g) + 3 H 2(g) 2 NH 3(g) 3. The form of an equation must match the K value. a) Consider H 2(g) + Br 2(g) 2 HBr (g) at 25° C. K = 1.9 × 10 19 = ] Br [ ] H [ ] HBr [ 2 2 2
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Chapter 14 Objectives (Chemical Equilibrium) Spring 2084 b) If 2 HBr (g) H 2(g) + Br 2(g) k = 2 2 2 ] HBr [ ] Br [ ] H [ = 5.3 × 10 -20 c) Note also that K changes if the temperature changes. d)
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This note was uploaded on 04/07/2008 for the course CHEM 0970 taught by Professor Kogut during the Spring '08 term at Pittsburgh.

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Chapter 14 notes - Chapter 14 Objectives(Chemical...

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