Chemistry 132 NTChemical EquilibriumReviewPowerPoint PresentationUsing the Equilibrium ConstantSlide 6Slide 7Slide 8Qualitatively Interpreting the Equilibrium ConstantSlide 10Slide 11Slide 12Slide 13Predicting the Direction of ReactionSlide 15Slide 16Slide 17Slide 18A Problem To ConsiderSlide 20Slide 21Slide 22Slide 23Calculating Equilibrium ConcentrationsSlide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Slide 53Operational SkillsHomeworkSlide 561111Chemistry 132 NTBe true to your work, your word, and your friend.Henry David Thoreau2222Chemical EquilibriumChapter 14Module 2Sections 14.4, 14.5, and 14.6Oscillating patterns formed by a reaction far from equilibrium3333ReviewEquilibrium and the equilibrium constant, Kc.Obtaining equilibrium constants for reactions.The equilibrium constant, Kp.Equilibrium constants for sums of reactions.Heterogeneous equilibrium.44445555Using the Equilibrium ConstantIn the last module, we looked at how a chemical reaction reaches equilibrium and how this equilibrium is characterized by an equilibrium constant.In this module, we will look at how we can use the equilibrium constant.6666Using the Equilibrium ConstantIn the last module, we looked at how a chemical reaction reaches equilibrium and how this equilibrium is characterized by an equilibrium constant.We’ll look at the following uses.1. Qualitatively interpreting the equilibrium constant .7777Using the Equilibrium ConstantIn the last module, we looked at how a chemical reaction reaches equilibrium and how this equilibrium is characterized by an equilibrium constant.We’ll look at the following uses.2. Predicting the direction of a reaction.8888Using the Equilibrium ConstantIn the last module, we looked at how a chemical reaction reaches equilibrium and how this equilibrium is characterized by an equilibrium constant.We’ll look at the following uses.3. Calculating equilibrium concentrations.9999Qualitatively Interpreting the Equilibrium ConstantAs stated in the last module, if the equilibrium constant is large, you know immediately that the products are favored at equilibrium.At 25oC the equilibrium constant equals 4.1 x 108.For example, consider the Haber process(g)2NH )g(H3)g(N32210101010Qualitatively Interpreting the Equilibrium ConstantAs stated in the last module, if the equilibrium constant is large, you know immediately that the products are favored at equilibrium.In other words, at this temperature, the reaction favors the formation of ammonia at equilibrium.For example, consider the Haber process(g)2NH )g(H3)g(N32211111111Qualitatively Interpreting the Equilibrium ConstantAs stated in the last module, if the equilibrium constant is small, you know immediately that the reactants are favored at equilibrium.For example, consider the reaction of nitrogen and oxygen to give nitric oxide, NO.2NO(g) )g(O)g(N22At 25oC the equilibrium constant equals 4.6 x 10-31.12121212Qualitatively Interpreting the Equilibrium ConstantAs stated in the last module, if the equilibrium constant is small, you know immediately that the reactants are favored at equilibrium.On the other hand, consider the reaction of nitrogen and oxygen to give nitric oxide, NO.2NO(g) )g(O)g(N22In other words, this reaction occurs to a very limited extent.13131313Qualitatively Interpreting the Equilibrium ConstantAs stated in the last module, if the equilibrium constant is small, you know immediately that the reactants are favored at equilibrium.On the other hand, consider the reaction of nitrogen and oxygen to give nitric oxide, NO.2NO(g) )g(O)g(N22(see Exercise 14.7 and Problems 14.47 and 14.49.)14141414Predicting the Direction of ReactionHow could one predict the direction in which a reaction at non-equilibrium conditions will shift to re-establish equilibrium?To answer this question, you substitute the current concentrations into the reaction quotient expression and compare it to Kc.The reaction quotient, Qc, is an expression that has the same form as the equilibrium-constant expression but whose concentrations are not necessarily at equilibrium.15151515Predicting the Direction of ReactionFor the general reactiondDcC bBaA  the Qc expression would be:badcc]B[]A[]D[]C[Qiiiiwhere the subscript “i” signifies initial or current concentrations.16161616Predicting the Direction of ReactionFor the general reactiondDcC bBaA  the Qc expression would be:badcc]B[]A[]D[]C[Qiiii If Qc > Kc, the reaction will shift left…toward reactants.17171717Predicting the Direction of ReactionFor the general reactiondDcC bBaA  the Qc expression would be:badcc]B[]A[]D[]C[Qiiii If Qc < Kc, the reaction will shift right… toward products.18181818Predicting the Direction of ReactionFor the general reactiondDcC bBaA  the Qc expression would be:badcc]B[]A[]D[]C[Qiiii If Qc = Kc, the reaction is at equilibrium and will not shift.19191919A Problem To ConsiderConsider the following equilibrium.A 50.0 L vessel contains 1.00 mol N2, 3.00 mol H2, and 0.500 mol NH3. In which direction (toward reactants or toward products) will the system shift in order to reestablish equilibrium at 400 oC?The Kc for the reaction at 400 oC is 0.500.(g)2NH )g(H3 )g(N32220202020A Problem To ConsiderFirst, calculate concentrations from moles of substances.(g)2NH )g(H3 )g(N3221.00 mol50.0 L3.00 mol50.0 L0.500 mol50.0 L212121210.0100 M0.0600 M0.0200 MA Problem To ConsiderFirst, calculate concentrations from moles of substances.(g)2NH )g(H3 )g(N322The Qc expression for the system would be:32223c]H][N[]NH[Q 222222220.0100 M0.0600 M0.0200 MA Problem To ConsiderFirst, calculate concentrations from moles of substances.(g)2NH )g(H3 )g(N322Substituting these concentrations into the reaction quotient gives:1.23)0600.0)(0200.0()0100.0(Q32c232323230.0100 M0.0600 M0.0200 MA Problem To ConsiderFirst, calculate concentrations from moles of substances.(g)2NH )g(H3 )g(N322Because Qc = 23.1 is greater than Kc = 0.500, the reaction will go to the left (toward reactants) as it approaches equilibrium.(see Exercise 14.8 and Problem 14.51)24242424Calculating Equilibrium ConcentrationsOnce you have determined the equilibrium constant for a reaction, you can use