1. Equilibrium Constant (K eq ) A constant which can tell you which side of an equilibrium is favored under certain conditions. A constant which can tell you which side of an equilibrium is favored under certain conditions. [http://cwx.prenhall.com/petrucci/medialib/media_portfolio/text_images/TB16_03.JPG]

2. Equilibrium Constant (K eq ) When K eq is large, reaction favors the products. When K eq is large, reaction favors the products. [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_15/FG15_07.JPG]

3. Equilibrium Constant (K eq ) When K eq is small, reaction favors the reactants. When K eq is small, reaction favors the reactants. [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_15/FG15_08.JPG]

4. [http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_15/FG15_18-04h.JPG] Which has the largest K eq ?

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6. Equilibrium Calculations The equilibrium constant can be used to calculate the concentrations (Molarity!) when a reaction reaches equilibrium. The equilibrium constant can be used to calculate the concentrations (Molarity!) when a reaction reaches equilibrium.

7. Equilibrium Calculations Example Reaction: Example Reaction: A + B ⇆ C + D A + B ⇆ C + D “[ ]” means molarity values!!!

8. Equilibrium Calculations Reactions with coefficients: Reactions with coefficients: 2 NO 2 (g) ⇆ N 2 O 4 (g) 2 NO 2 (g) ⇆ N 2 O 4 (g) Coefficient becomes a power!

9. Equilibrium Calculations Include only gases and aqueous solutions (aq): Include only gases and aqueous solutions (aq): C (s) + H 2 O (g) ⇆ CO (g) + H 2 (g) C (s) + H 2 O (g) ⇆ CO (g) + H 2 (g) Solids not included!

10. Equilibrium Calculations Example: Example: H 2 (g) + I 2 (g) ⇆ 2 HI (g) H 2 (g) + I 2 (g) ⇆ 2 HI (g) If the concentrations are: If the concentrations are: – H 2 =0.10 M – I 2 =0.10 M – HI=0.20 M – What is K eq ?

12. Reaction Quotient (Q) Calculation for the reaction and compare to K eq to see if a reaction has reached equilibrium. Calculation for the reaction and compare to K eq to see if a reaction has reached equilibrium.

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14. Reaction Quotient (Q) Example: Example: 2 NO 2 (g) ⇆ N 2 O 4 (g) 2 NO 2 (g) ⇆ N 2 O 4 (g) If the concentrations are: If the concentrations are: – NO 2 = 0.150 M – N 2 O 4 = 0.300 M – What is Q? – If K eq = 4.73, is the reaction at equilibrium?

16. Reaction Quotient (Q) Reaction is not at equilibrium… Reaction is not at equilibrium… Q (13.3) > K eq (4.73), so reaction is shifting towards the reactants. Q (13.3) > K eq (4.73), so reaction is shifting towards the reactants.