Le Châtelier and His Principle

Warm-Up (1) A mixture of H 2 and I 2 is allowed to react at 448 o C. When equilibrium is established, the concentrations of the participants are found to be [H 2 ] = 0.46 M, [I 2 ] = 0.39 M, and [HI] = 3.0 M. Calculate the value of the K eq at 448 o C. H 2 (g) + I 2 (g) HI(g) (2) Solid iron metal reacts with water vapor to produce solid iron (III) oxide and hydrogen gas. At equilibrium the concentration of water is 1.0 M, and the concentration of the hydrogen gas is = 4.5 M. Calculate the value of the K eq.

Homework Answers EQUILIBRIUM: [SO 3 ] 2 (1) Keq = (2) n/a = all liquids [SO 2 ] 3 [O 2 ] 1[CH 4 ] [H 2 O] (3) Keq = (4) Keq = [H 2 ] 2 [O 2 ][H 2 ] 3 [CO] (5) Keq = [CO 2 ]

Homework Answers (6) (7) Keq < 1 thus reactants favored (8) 4.01 (9) 0.50 (10) 1.41 M (11) (12) 9.81 X ( )

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The Week Ahead…. DayWhat We’ll Be Doing Mon / Tues  Unit 11 – Equilibrium Wed  Unit 11 QUIZ (Grade)  Reference Table Scavenger Hunt (Grade)  Exam Review Day 1 Thurs  Exam Review Packet – Grade Sheet #1  Take/Discuss Released Test (Short Version)  Exam Review Day 2 Fri  Exam Review Packet – Grade Sheet #2  Cumulative Review Demo – Post-Test (Grade)  Exam Review Day 3 Mon  Exam Review Packet – Grade Sheet #3  Take/Discuss Released Test (Long Version)  Exam Review Day 4 Tues  Exam Review Packet – Grade Sheet #4  Cumulative Review Activity  Final Exam Reminders

Le Châtelier’s Principle If a stress is applied to a system at equilibrium, the system shifts to reduce the stress.

The 3 stresses of Chemistry 1. Concentration 2. Temperature 3. Pressure REACTANTS PRODUCTS

Concentration Increasing the concentration of one of the reactants or products causes a shift toward the other side. Decreasing the concentration of one of the reactants or products causes a shift toward the same side.

Temperature Treat heat as a product for exothermic Treat heat as a reactant for endothermic Refer back to rules for concentration

Pressure Note-only applies if there is an unequal amount of gases on each side Increasing the pressure will cause a shift toward the side with the lower number of moles of gas. Decreasing the pressure will cause a shift toward the side with the higher number of moles of gas.

12.6 J + H 2 (g) + I 2 (g)  2HI (g) How would the equilibrium shift when the following stresses are applied to the system? (1) Add hydrogen iodide (2) Increase the temperature (3) Decrease the pressure (4) Remove Iodine LEARNING TEAM CHALLENGE #1

Learning Team Challenge N 2 (g) + H 2 (g) ⇆ NH 3 (g) Would the equilibrium shift toward the reactants OR products if…… Hydrogen was removed? Ammonia was added? Hydrogen was added? Pressure was increased?

UNIVERSITY OF EQUILIBRIUM hemistry_lechateliers/index.html CAN YOU GRADUATE WITH HONORS? Hawkins’ Wiki Page – January 5 – Click on the Link for University of Equilibrium - Start with Year 1 - Complete Years 1 – 4 - Take Final Exam – show Hawkins’ Score

You try! C 2 H 2 (g) + H 2 O (g) ⇆ CH 3 CHO (g) The above reaction is endothermic, predict the shift in the equilibrium (1) You increase CH 3 CHO (2) You decrease C 2 H 2 (3) You increase H 2 O (4) You decrease the temperature

Goals You should now be able to… Predict what side of the reaction will be favored given a stressor

Exit Ticket For the equilibrium system (1) Write the equation for the calculating the equilibrium constant How will the above reaction shift if: (2) More chlorine is added? (3) Pressure is increased (note: all reactants and products are gases) BONUS: Keq = 35. If the concentrations of PCl 5 and PCl 3 are 0.025M and 0.68M respectively, what is the concentration of the Cl 2 ?

HOMEWORK  Worksheet Equilibrium: #13 Le Chatelier’s Principle: ALL (1 – 5) – omit 2 D UNIT 11 QUIZ TOMORROW !!  BRING YOUR ORGANIZED NOTEBOOK TOMORROW TO BEGIN EXAM REVIEW!!

After School Tutoring DAYUNITSTOPICS MON 2 & 3 Subatomic particles, Avg Atomic Mass, Nuclear Decay, Half-life, Electron Notations, Reading Bohr Model of H, Periodic Table, Periodic Trends TUES Chemical Bonding, VSEPR, IMFs, Chemical Nomenclature/Formulas, Mole Math, Emp. and Molec Formulas, Types of Chem Rxns, Predicting Products for Chem Rxns, Net Ionic Equations, Energy of Rxns

After School Tutoring DAYUNITSTOPICS THURS Stoichiometry, Limiting Reactants, % Yield, States of Matter, Phase Changes, Effects of pressure, Temp/Pressure Conversions, Combined Gas Law, Ideal Gas Law, Dalton’s Law of Partial Pressure, Molarity, Solution Dilution, Reading Solubility Curves FRI 10 & 11 Properties of Acids/Bases, Naming Acids/Bases, pH & pOH, Titrations, Equilibrium