Lecture 43 Equilibrium 4 Read HW BLB 15 6 15 7 BLB 15 51 53 70 Sup 15 11 13 Know LeChatelier s principle catalysts math refresher in BLB Appendix A Need help Get help TAs in CRC 211 Whitmore and SI hours on Chem 110 website my office hours Mon 12 30 2 Tues 10 30 12 in 324 Chem Bldg or 326 Chem THIS week is last week for SI CRC and Sheets Office Hours Final Exam MONDAY May 4 12 20 pm locations under exam schedule no pds ipods graphing calculators etc Only non text programmable calculators allowed Bring PSU ID and pencils Concept Final review session with Sheets Thursday 4 30 6pm in 108 Forum Please work through the Concept Exam on lecture note page before the review session bring it with you along with any questions you may have This review is meant to complement to the review sessions that your TAs will be holding in which they will go over the practice exams good luck may the Chemistry gods smile upon you Sheets Page 1 Lecture 43 Chem 110 lays the foundation What we ve covered this semester Atoms Molecules Interactions between the Same Molecules Interactions between Different Molecules Reactions Thermochemistry Equilibria Structure of atoms molecules controls their properties functions Energy changes tell us about changes in electronic transitions molecular or ionic properties reactions Sheets Page 2 Lecture 43 LeChatelier s principle an example to illustrate this principle the following chemical system is in a closed 1 0 L container 4 HBr g O2 g 2 H2O g 2 Br2 g Hrxn 466 kJ initial conditions T 500 K HBr 4 0 M O2 1 0 M H2O 0 0 M Br2 0 0 M at equilibrium HBr 1 0 M O2 0 25 M H2O 1 5 M Br2 1 5 M What is Kc Sheets Kc Page 3 Lecture 43 LeChatelier s principle an example cont For the following reaction 4 HBr g O2 g 2 H2O g 2 Br2 g A What will happen to Br2 if 4 0 moles of HBr are added to the system which is at equilibrium System is no longer at equilibrium Which direction will it go to get to equilibrium Using LeChatelier s principle reactant or product added to a mixture at equilibrium will cause reaction to shift in the direction that consumes part of the added material Q Sheets Page 4 Lecture 43 Applying LeChatelier s principle an example For the following reaction 4 HBr g O2 g 2 H2O g 2 Br2 g B What will happen if the volume decreases from 1 0 L to 0 5 L n as V V so Px X RT partial P Using LeChatelier s principle since pressure is increased by disturbance reaction will shift in direction that will reduce pressure 4 HBr g O2 g 5 mol total Sheets 2 H2O g 2 Br2 g 4 mol total Page 5 Lecture 43 LeChatelier s principle an example cont C What will happen if 5 0 moles of inert gas is added to the system inert gas gas that does NOT participate in the reaction How does inert gas effect concentrations of reactants products 4 HBr g O2 g 2 H2O g 2 Br2 g Using LeChatelier s principle Sheets Page 6 Lecture 43 Summarizing LeChatelier s principle so far changing concentration or V so that changes or P changes puts a stress on the system stresses do not change Keq Q changes system shifts to re establish equilibrium Q K BUT what if temperature changes Keq does depend on temperature change depends on whether the reaction is exothermic H is or endothermic H is Sheets Page 7 Lecture 43 LeChatelier s principle an example cont For the following reaction 4 HBr g O2 g 2 H2O g 2 Br2 g D What will happen if the temperature is increased to 1000 K 4 HBr g O2 g 2 H2O g 2 Br2 g Hrxn 466 kJ treat heat as a product if exothermic or as a reactant if endothermic review Lecture 38 Using Le Chatelier s principle when heat is added to a system reaction shifts in the direction that absorbs heat for this particular reaction which is exothermic heat is a product adding heat will cause reaction to shift to left Sheets Page 8 Lecture 43 Back to the Haber process cont N2 g 3H2 g 2NH3 g heat This system is at equilibrium What will happen to NH3 if Sheets add N2 NH3 remove H2 NH3 raise T NH3 increase P NH3 decrease V NH3 add catalyst NH3 Page 9 Lecture 43 Example from old exam 5 CO g I2O5 g I2 g 5 CO2 g H 1175 kJ For this reaction at equilibrium which of the changes will NOT have any effect on the equilibrium concentrations of reactants or products A adding more CO g to the mixture B increasing the pressure by decreasing the volume of the container C removing some of the I2 g D raising the temperature of the mixture E adding more I2O5 g Sheets Page 10 Lecture 43 Example from old exam 5 CO g I2O5 g I2 s 5 CO2 g H 1237 kJ For this reaction at equilibrium which of the changes will NOT have any effect on the equilibrium concentrations of reactants or products A adding more CO g to the mixture B increasing the pressure by decreasing the volume of the container C removing some of the I2 s D raising the temperature of the mixture E adding more I2O5 g Sheets Page 11 Lecture 43 Example from old exam Consider the following reaction CO g H2O g CO2 g H2 g Kc 2 7 If 0 153 mole CO 0 546 mole H2O 0 262 mole CO2 and 0 743 mole H2 are introduced into a 2 0 L vessel which of the following statements will be true A The system is at equilibrium and no change will occur B The system is not at equilibrium and will proceed to the right to achieve equilibrium C The system is not at equilibrium and will proceed to the left to achieve equilibrium D The system is not at equilibrium and it cannot achieve equilibrium E The system is at equilibrium but the addition of a catalyst will cause the reaction to proceed to the right Sheets Page 12 Lecture 43 Example Consider the hypothetical reaction A g 2 B g A flask is charged with 0 55 atm of pure A after which it is allowed to reach equilibrium at 0 C At equilibrium the partial pressure of A is 0 36 atm What is the total pressure in the flask at equilibrium What is the value of Kp initial change final Sheets A 0 55 atm B consumed 0 36 atm produced Page 13 Lecture 43 Before next class Review entire semester Please bring any last minute questions you may have This is for touch up or clarification questions NOT a lecture repeat Print out the question so I can put up on the document reader as we ve done previously before …
View Full Document
Unlocking...