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Previously in Chem 104: Kinetics

Previously in Chem 104: Kinetics. TODAY A new chapter, a new idea?. A moment of review: Big Ideas in Chemistry. 1. Structure determines Behavior. 2. Equilibrium and. Le Chatelier’s Principle. TODAY A new chapter: Equilibrium Writing equilibrium expressions

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Previously in Chem 104: Kinetics

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  1. Previously in • Chem 104: • Kinetics • TODAY • A new chapter, a new idea? A moment of review: Big Ideas in Chemistry 1. Structure determines Behavior 2. Equilibrium and Le Chatelier’s Principle

  2. TODAY • A new chapter: Equilibrium • Writing equilibrium expressions • Disturbing Equilibrium; observing LeChatelier’s Principle • Calculating equilibrium constants, K

  3. At the end of Kinetics Chapter, this was introduced: k1 k-1 N2O2 NO + NO Dynamic EQUILIBRIUM applet

  4. At the end of Kinetics Chapter, this was introduced: k1 k-1 N2O2 NO + NO And; Forward rate k1 Keq or Backward rate k-1

  5. What does the value of Keq tell us? k1 NO + NO k-1 N2O2 If: Fast forward rate 103 M sec-1 like 10-13 M sec-1 Slow backward rate Reaction “lies” towards products, Keq is LARGE

  6. What does the value of Keq tell us? k1 NO + NO k-1 N2O2 If: Slow forward rate 10-13 M sec-1 like 10-3 M sec-1 Fast backward rate Reaction “lies” towards reactants, Keq is small: We say reaction doesn’t “go”.

  7. Are rate constants the only way to get Keq? NO ! [products] Keq [reagents] For: NO + NO N2O2 [N2O2] Keq [NO]2

  8. More generally Keq is defined as: [products] Keq [reagents] For: aA + bB cC + dD [C]c[D]d Keq [A]a[B]b That’s all you need know in Chapter 16.

  9. What is this Copper experiment about? EQUILIBRIUM EQUILIBRIUM EQUILIBRIUM EQUILIBRIUM Closely followed by Le Chatelier’s Principle “ a system at equilibrium when disturbed will adjust to remove or minimize the effect of the disturbance”

  10. The series of reactions observed: 1. CuCl2(H2O)2(s) + 3H2O [CuCl(H2O)5]+ + Cl- 2. [CuCl(H2O)5]+ + H2O [Cu(H2O)6]2++ Cl- 3. [Cu(H2O)6]2++ Cl- [CuCl(H2O)5]2++ H2O

  11. What is first equilibrium expression: [products] Keq [reagents] [Cu(H2O)6]2++ Cl- [CuCl(H2O)5]++ H2O [CuCl(H2O)5+][H2O] Keq [Cu(H2O)62+][Cl] But, pure liquids don’t appear in Keq expression: [CuCl(H2O)5+] Keq [Cu(H2O)62+][Cl]

  12. The series of reactions observed: 1. CuCl2(H2O)2(s) + 3H2O [CuCl(H2O)5]+ + Cl- 2. [CuCl(H2O)5]+ + H2O [Cu(H2O)6]2++ Cl- 3. [Cu(H2O)6]2++ Cl- [CuCl(H2O)5]2++ H2O [CuCl(H2O)52+] Keq [Cu(H2O)62+][Cl] 0.80 M Keq 0.28, NO UNITS! 0.40M x 7.1 M

  13. Combining reactions equals multiplying K’s (a) CuCl2(H2O)2(s) + 3H2O [CuCl(H2O)5]+ + Cl- K1eq (b) [CuCl(H2O)5]+ + H2O [Cu(H2O)6]2++ Cl- K2eq Kneteq Net CuCl2(H2O)2(s) + 4H2O [Cu(H2O)6]2++ 2 Cl- [CuCl(H2O)52+ [Cl] [Cu(H2O)62+][Cl] K1eq x K2eq [CuCl(H2O)52+] CuCl2(H2O)2(s) Pure solids don’t appear in Keq [Cu(H2O)62+][Cl]2 [Cu(H2O)62+][Cl]2 Kneteq CuCl2(H2O)2(s)

  14. What was this Copper experiment about? EQUILIBRIUM EQUILIBRIUM EQUILIBRIUM EQUILIBRIUM Closely followed by Le Chatelier’s Principle “ a system at equilibrium when disturbed will adjust to remove or minimize the effect of the disturbance”

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