CHAPTER 13: EQUILIBRIUM Outline 1. introduction; definition; examples 2. KC, KP, example 3. heterogeneous equilibria; examples 4. size of K, extent of reaction 5. predicting the direction of a reaction; Q 6. calculations with K determining K from data determining equilibrium concentrations from K 7. factors that affect equilibrium: LeChatelier’s Principle

review topics: yields of chemical reactions: Chapter 3 Section 5 stoichiometry: Chapter 3 Section 4 partial pressure: Chapter 9 Section 5

EQUILIBRIUM: PART 1 1. A reaction that proceeds to completion a. has a theoretical yield greater than the actual yield. b. has a theoretical yield less than the actual yield. c. has a theoretical yield equal to the actual yield. 2. True/False: All chemical reactions proceed to completion assuming the experimenter’s technique is perfect.

Demonstration: phenolphthalein added to 0.1M NaOH (solution A) 0.1M HCl added to 0.1M NaOH w/ phenolphthalein (=solution B) 0.1M NaOH added to solution B (=solution C) 0.1M HCl added to solution C observations phenolphthalein, C20H14O4

solution A: C20H14O4(colorless) + OH1-  C20H13O41-(pink) + H2O solution B: C20H13O41-(pink) + H1+  C20H14O4(colorless) or C20H14O4(colorless) + OH1-  C20H13O41-(pink) + H2O or C20H13O41-(pink) + H1+  C20H14O4(colorless)

3. What physiological reaction in blood is reversible?

Thought experiment: 1. Add solid sodium iodide to water till no more sodium iodide dissolves. Filter. 2. Purchase radioactively-labeled NaI(s). 3. Add the solid radioactively-labeled NaI(s) to the saturated solution of NaI(aq). Wait one day. Filter. What would you observe?

chemical equilibrium: the concentrations of reactants & products in a chemical reaction remain constant chemical reactions are reversible chemical equilibrium is dynamic Questions: How do we predict the concentrations of products and reactants at equilibrium? (Chapters 13, 15, 16) Why is it important to be able to predict equilibrium concentrations? Why do some reactions proceed nearly to completion but others result in a mixture of products and reactions? (Chapter 17) entropy