Chapter 13.1-13.4 AP Chem Chemical Equilibrium

13.1 The Equilibrium Condition 13.2 The Equilibrium Constant Chapter 13 Table of Contents 13.1 The Equilibrium Condition 13.2 The Equilibrium Constant 13.3 Equilibrium Expressions Involving Pressures 13.4 Heterogeneous Equilibria 13.5 Applications of the Equilibrium Constant 13.6 Solving Equilibrium Problems 13.7 Le Châtelier’s Principle Copyright © Cengage Learning. All rights reserved

*Be sure all reports are turned in and made up TODAY! Chapter 13 Table of Contents WEEK OUTLOOK Monday - Notes 13.1-13.4 with problems w/sheet due Tuesday - should be able to complete in class today. *Be sure all reports are turned in and made up TODAY! Tuesday - Notes 13.5-13.7 with emphasis on Le Chatelier’s Principle emphasized & problems assigned due Wed. - some time in class to complete Kaci & Jonathan - library 2nd floor 7:30 with ACT invent. Wednesday- Lab Thursday - CAPS - No class Friday - Good Friday - No school Tuesday - April 2nd - ACT Testing 11th graders only. Test probably next Thursday - just over ch. 13 only. Copyright © Cengage Learning. All rights reserved 3

HANDOUT - Equilibrium Homework Sheet #1 Chapter 13 Table of Contents HANDOUTS - Ch. 13 NMSI Equilibrium Packet (Notes with practice problems) HANDOUT - Equilibrium Homework Sheet #1 TURN IN Kinetics Lab - will go over pre-lab questions HW: Equilibrium w/s #1 should be done today - due Mon. for grade HW: Notes packet #1-6 problems due next week but keep for studying. CW: Notes 13.1-13.4 VOTE ON KINETICS TESTING CH. 12 Iodine Clock Rxn. Simulation Lab - as time permits Copyright © Cengage Learning. All rights reserved

Dynamic Nature of Equilibrium When a system reaches equilibrium, the forward and reverse reactions continue to occur … but at equal rates. We are usually concerned with the situation after equilibrium is reached. After equilibrium the concentrations of reactants and products remain constant. Prentice Hall © 2005 Chapter Fourteen General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry

Section 13.1 The Equilibrium Condition Chemical Equilibrium The state where the concentrations of all reactants and products remain constant with time. On the molecular level, there is frantic activity. Equilibrium is not static, but is a highly dynamic situation. Return to TOC Copyright © Cengage Learning. All rights reserved

Macroscopically static Microscopically dynamic Section 13.1 The Equilibrium Condition Equilibrium Is: Macroscopically static  Microscopically dynamic Return to TOC Copyright © Cengage Learning. All rights reserved

Changes in Concentration Section 13.1 The Equilibrium Condition Changes in Concentration N2(g) + 3H2(g) 2NH3(g) Return to TOC Copyright © Cengage Learning. All rights reserved

Section 13.1 The Equilibrium Condition Chemical Equilibrium Concentrations reach levels where the rate of the forward reaction equals the rate of the reverse reaction. Return to TOC Copyright © Cengage Learning. All rights reserved

The Changes with Time in the Rates of Forward and Reverse Reactions Section 13.1 The Equilibrium Condition The Changes with Time in the Rates of Forward and Reverse Reactions Return to TOC Copyright © Cengage Learning. All rights reserved

H2O(g) + CO(g) H2(g) + CO2(g) Section 13.1 The Equilibrium Condition Concept Check Consider an equilibrium mixture in a closed vessel reacting according to the equation: H2O(g) + CO(g) H2(g) + CO2(g) You add more H2O(g) to the flask. How does the concentration of each chemical compare to its original concentration after equilibrium is reestablished? Justify your answer. The concentrations of each product will increase, the concentration of CO will decrease, and the concentration of water will be higher than the original equilibrium concentration, but lower than the initial total amount. Students may have many different answers (hydrogen goes up, but carbon dioxide in unchanged, etc.) Let them talk about this for a while – do not go over the answer until each group of students has come up with an explanation. This question also sets up LeChâtelier’s principle for later. Return to TOC Copyright © Cengage Learning. All rights reserved

H2O(g) + CO(g) H2(g) + CO2(g) Section 13.1 The Equilibrium Condition Concept Check Consider an equilibrium mixture in a closed vessel reacting according to the equation: H2O(g) + CO(g) H2(g) + CO2(g) You add more H2 to the flask. How does the concentration of each chemical compare to its original concentration after equilibrium is reestablished? Justify your answer. This is the opposite scenario of the previous slide. The concentrations of water and CO will increase. The concentration of carbon dioxide decreases and the concentration of hydrogen will be higher than the original equilibrium concentration, but lower than the initial total amount. Return to TOC Copyright © Cengage Learning. All rights reserved

Consider the following reaction at equilibrium: Section 13.2 Atomic Masses The Equilibrium Constant Law of Mass Action Consider the following reaction at equilibrium: jA + kB lC + mD A, B, C, and D = chemical species. Square brackets = concentrations of species at equilibrium. j, k, l, and m = coefficients in the balanced equation. K = equilibrium constant (given without units). l m [C] [D] K = [A] j [B] k Return to TOC Copyright © Cengage Learning. All rights reserved

Conclusions About the Equilibrium Expression Section 13.2 The Equilibrium Constant Atomic Masses Conclusions About the Equilibrium Expression Equilibrium expression for a reaction is the reciprocal of that for the reaction written in reverse. When balanced equation for a reaction is multiplied by a factor of n, the equilibrium expression for the new reaction is the original expression raised to the nth power; thus Knew = (Koriginal)n. K values are usually written without units. Return to TOC Copyright © Cengage Learning. All rights reserved

Conclusions about Equilibrium Expressions The equilibrium expression for a reaction is the reciprocal for a reaction written in reverse 2NO2(g)  2NO(g) + O2(g) 2NO(g) + O2(g) 2NO2(g)

Conclusions about Equilibrium Expressions When the balanced equation for a reaction is multiplied by a factor n, the equilibrium expression for the new reaction is the original expression, raised to the nth power. 2NO2(g)  2NO(g) + O2(g) NO2(g)  NO(g) + ½O2(g)

Equilibrium position is a set of equilibrium concentrations. Section 13.2 Atomic Masses The Equilibrium Constant K always has the same value at a given temperature regardless of the amounts of reactants or products that are present initially. For a reaction, at a given temperature, there are many equilibrium positions but only one value for K. Equilibrium position is a set of equilibrium concentrations. Return to TOC Copyright © Cengage Learning. All rights reserved

K involves concentrations - (also called Kc) Section 13.3 Equilibrium Expressions Involving Pressures The Mole K involves concentrations - (also called Kc) Kp involves pressures for gases. Return to TOC Copyright © Cengage Learning. All rights reserved

N2(g) + 3H2(g) 2NH3(g) Equilibrium Expressions Involving Pressures Section 13.3 Equilibrium Expressions Involving Pressures The Mole Example N2(g) + 3H2(g) 2NH3(g) Return to TOC Copyright © Cengage Learning. All rights reserved

Equilibrium pressures at a certain temperature: Section 13.3 Equilibrium Expressions Involving Pressures The Mole Example N2(g) + 3H2(g) 2NH3(g) Equilibrium pressures at a certain temperature: Return to TOC Copyright © Cengage Learning. All rights reserved

N2(g) + 3H2(g) 2NH3(g) Equilibrium Expressions Involving Pressures Section 13.3 Equilibrium Expressions Involving Pressures The Mole Example N2(g) + 3H2(g) 2NH3(g) Return to TOC Copyright © Cengage Learning. All rights reserved

The Relationship Between K and Kp Section 13.3 Equilibrium Expressions Involving Pressures The Mole The Relationship Between K and Kp Kp = K(RT)Δn Δn = sum of the coefficients of the gaseous products minus the sum of the coefficients of the gaseous reactants. R = 0.08206 L·atm/mol·K T = temperature (in kelvin) Return to TOC Copyright © Cengage Learning. All rights reserved

Section 13.3 Equilibrium Expressions Involving Pressures The Mole Example N2(g) + 3H2(g) 2NH3(g) Using the value of Kp (3.9 × 104) from the previous example, calculate the value of K at 35°C. Return to TOC Copyright © Cengage Learning. All rights reserved

Homogeneous Equilibria Section 13.4 Heterogeneous Equilibria Homogeneous Equilibria Homogeneous equilibria – involve the same phase: N2(g) + 3H2(g) 2NH3(g) HCN(aq) H+(aq) + CN-(aq) Return to TOC Copyright © Cengage Learning. All rights reserved

Heterogeneous Equilibria Section 13.4 Heterogeneous Equilibria Heterogeneous Equilibria Heterogeneous equilibria – involve more than one phase: 2KClO3(s) 2KCl(s) + 3O2(g) 2H2O(l) 2H2(g) + O2(g) Return to TOC Copyright © Cengage Learning. All rights reserved

The concentrations of pure liquids and solids are constant. Section 13.4 Heterogeneous Equilibria The position of a heterogeneous equilibrium does not depend on the amounts of pure solids or liquids present. The concentrations of pure liquids and solids are constant. 2KClO3(s) 2KCl(s) + 3O2(g) Return to TOC Copyright © Cengage Learning. All rights reserved

Equilibria Involving Pure Solids and Liquids The equilibrium constant expression does not include terms for pure solid and liquid phases because their concentrations do not change in a reaction. Although the amounts of pure solid and liquid phases change during a reaction, these phases remain pure and their concentrations do not change. Example: CaCO3(s) CaO(s) + CO2(g) [CaO] [CO2] Kc = –––––––––– [CaCO3] Kc = [CO2] Prentice Hall © 2005 Chapter Fourteen General Chemistry 4th edition, Hill, Petrucci, McCreary, Perry

Heterogeneous Equilibria ASSIGNMENTS - 2/20/14 Section 13.4 Heterogeneous Equilibria W/sheet #1 problems due Monday This assignment should be able to be completed today in class but is due Monday. Ch. 13 Equilibrium packet - #1-#6 practice problems - answers shown to see if you are doing correctly. Prepare for Test on Kinetics. HW: Read chapter 13 over the next week. Ch. 12 Kinetics Test - VOTED for WEDNESDAY - Feb 26 Return to TOC Copyright © Cengage Learning. All rights reserved