Lec-19-Exam2Review

Lec-19-Exam2Review - Lec-19: Second Midterm Review Be sure...

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Unformatted text preview: Lec-19: Second Midterm Review Be sure to bring the following: Stony Brook ID card 2 or more #2 pencils and a good eraser Calculator with extra batteries 1 Tuesday October 18th, 8:30 10:00 PM Solar ID Room 000000000 107757371 Javits 100 Main Floor 107757372 999999999 Javits 100 Balcony Room Assignments Equilibrium Constants: General Case Kc allows us to answer questions concerning: At equilibrium , do reactants or products predominate? Given initial/equilibrium concentrations of reactants/products, determine the value of Kc. Given initial concentrations of reactancts and products , in which way does the reaction proceeds? What are the concentrations of reactant and products at equilibrium? C+ D+ A+ B+ a b c d L L [ ] [ ] [ ] [ ] D A B C c d a b c K = L L 2 Equilibrium Constants: reactions with pure phases or solvent participation ( 29 ( 29 ( 29 ( 29 [ ] 4 3 3 4 2 NH aq OH aq NH aq N H H H O N H O c K +- +- + = + l ( 29 ( 29 ( 29 [ ] 2 3 CO 2 2 CaO s CO g O O s C CaC p c K P K + = = The only concentrations that appear in the equilibrium constant expression are those of gases and of solutes in dilute solutions 3 Equilibrium Constants: multiplying reaction equations The numerical value of the two equilibrium constants is very different . ( 29 ( 29 ( 29 [ ] [ ][ ] 2 2 1 2 2 2 2 2 H O H O g 1 H g O g 2 + H O c K = ( 29 ( 29 ( 29 [ ] [ ] [ ] 2 2 2 2 2 2 2 2 H O 2H O g 2H g O g + H O c K = [ ] [ ] [ ] [ ] [ ][ ] ( 29 2 1 2 2 2 2 2 2 2 2 2 2 H O H H O O H O c c K K = = = 4 5 More generally, if for a reaction C+ D+ A+ B+ a b c d L L [ ] [ ] [ ] [ ] D A B C c d a b c K = L L ( 29 ( 29 * A+ B+ C+ D+ b c f a d L L [ ] [ ] [ ] [ ] D B ' A C c d f f c f f a b K = L L If then 1 f = - ( 29 1 1 ' c c c K K K- = = [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] ( 29 C D C D A B A ' B f f f f c c f f b c a c b d a d K K = = = L L L L We then have Equilibrium Constants: Combined Reactions ( 29 ( 29 ( 29 [ ] [ ][ ] ( 29 ( 29 ( 29 [ ] [ ] [ ] 1 2 2 2 2 2 2 2 2 2 2 2 2 N g O g N O 2NO NO 2NO g NO 2 NO g g O g + NO O c c K K = + = ( 29 ( 29 ( 29 [ ] [ ][ ] 2 2 2 2 2 2 2 2 NO 2NO g N g 2O g N O c K = + [ ] [ ][ ] [ ] [ ][ ] [ ] [ ] [ ] 2 2 2 2 2 2 2 2 2 2 2 2 2 1 N O N O NO N NO NO O O c c c K K K = = = 6 Multiplication Sum of chemica of equilibrium l rea con c s ti ns s o tant Chemical Equilibrium Gas phase reactions For reactions in gas phase, at low pressure, we can write for the partial pressure of each substance [ ] A A A R n V P T RT = = Replacing in Kc in terms of the partial pressures: ( 29 ( 29 ( 29 A B C D , a b c c d n p P P K R a c d P K n T b P = = + +- + = + L L L L Then, for chemical reactions in the gas phase we can choose to work with [ ] [ ] [ ] [ ] C D A B C D o A B r c p c d c d a b a b K P P P K P = = L L L L 7 8 ( 29...
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Lec-19-Exam2Review - Lec-19: Second Midterm Review Be sure...

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