1. Tutorial on Le Chateliers Principle,Equilibrium Law, Position of Equilibriumand Equilibrium Constant . Prepared by Lawrence Kok http://lawrencekok.blogspot.com

2. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established again Effect of Concentration on the position of equilibrium Increase in Conc - position of equilibrium shift to right/left - Conc will be Reduced Decrease in Conc position of equilibrium shift to right/left - Conc will be Increased Fe3+ + SCN- Fe(SCN)+2(yellow)(red Blood)Click to view videoIncrease SCN- or Fe3+ Conc Decrease Fe3+ Conc Decrease SCN- Conc 3. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established againEffect of Concentration on the position of equilibrium Increase in Conc - position of equilibrium shift to right/left - Conc will be Reduced Decrease in Conc position of equilibrium shift to right/left - Conc will be Increased Fe3+ + SCN- Fe(SCN)+2(yellow)(red Blood)Click to view videoIncrease SCN- or Fe3+ Conc Decrease Fe3+ ConcEquilibrium shift to right By adding OH- will shift equilibrium to left Formation of complex ion Fe(SCN)2+ (red blood)Fe(SCN)2+ breakdown to form more Fe3+ (yellow) Decrease SCN- Conc By adding Ag+ will shift equilibrium to left Fe(SCN)2+ breakdown to form more SCN- (yellow) Increase Concentration Rate of reaction increase Rate constant - no change Kc, equilibrium constant - no changes Position of equilibrium shifted to a side to decrease concentration again 4. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established again Effect of Concentration on the position of equilibrium Increase in Conc - position of equilibrium shift to right/left - Conc will be Reduced Decrease in Conc position of equilibrium shift to right/left - Conc will be Increased 2CrO42- + 2H+ Cr2O72- + H2O(yellow)(orange)Click to view videoDecrease H+ Conc Increase H+ Conc 5. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established againEffect of Concentration on the position of equilibrium Increase in Conc - position of equilibrium shift to right/left - Conc will be Reduced Decrease in Conc position of equilibrium shift to right/left - Conc will be Increased 2CrO42- + 2H+ Cr2O72- + H2O (yellow)(orange) Click to view videoDecrease H+ ConcIncrease H+ Conc By adding OH- By adding H+Equilibrium shift to left Shift equilibrium to right Formation of CrO42- (yellow) Formation of Cr2O72- (orange) Increase Concentration Rate of reaction increase Rate constant - no change Kc, equilibrium constant - no changes Position of equilibrium shifted to a side to decrease concentration again 6. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established again Effect of Concentration on the position of equilibrium Increase in Conc - position of equilibrium shift to right/left - Conc will be Reduced Decrease in Conc position of equilibrium shift to right/left - Conc will be Increased CoCl42- + 6H2O Co(H2O)62+ + 4CI (blue)(pink) Click to view videoDecrease CI- Conc Increase H2O ConcIncrease CI- Conc 7. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established again Effect of Concentration on the position of equilibrium Increase in Conc - position of equilibrium shift to right/left - Conc will be Reduced Decrease in Conc position of equilibrium shift to right/left - Conc will be Increased CoCl42- + 6H2O Co(H2O)62+ + 4CI (blue)(pink)Click to view videoDecrease CI- Conc Increase H2O Conc Increase CI- ConcBy adding Ag+ to form AgCI By adding H2O By adding HCIEquilibrium shift to right Shift equilibrium to right Shift equilibrium to left Formation of Co(H2O)62+ (pink) Formation of Co(H2O)62+ (pink) Formation of CoCl42- (blue) Increase Concentration Rate of reaction increase Rate constant - no change Kc, equilibrium constant - no changes Position of equilibrium shifted to a side to decrease concentration again 8. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established againEffect of Pressure on the position of equilibriumIncrease in pressure - favour reaction with a decrease in pressure Decrease in pressure - favour reaction with an increase in pressure N2O4 (g) 2NO2(g) (colourless) (brown)Click to view videoIncreasing Pressure Decreasing Pressure 9. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancelout the effect of change and a new equilibrium can be established againEffect of Pressure on the position of equilibrium Increase in pressure - favour reaction with a decrease in pressure Decrease in pressure - favour reaction with an increase in pressure N2O4 (g) 2NO2(g)(colourless)(brown)Click to view videoIncreasing Pressure Decreasing Pressure By reducing Volume By Increasing Volume Equilibrium shift to left Equilibrium shift to right Less molecules on left side More molecules on right sidePressure drops Pressure increase Formation of N2O4 (colourless) Formation of NO2 (brown) Increase Pressure Rate of reaction increases Rate constant unchanged Position of equilibrium shift to reduce pressure Kc, equilibrium constant unchangedIncrease pressure collision more frequent - shift equilibrium to left - to reduce number of molecules - pressure decrease again Decrease pressure collision less frequent shift equilibrium to right to increase number of molecules pressure increase again 10. Factors affecting the position of Equilibrium Effect of Pressure on the position of equilibriumIncrease in pressure - favour reaction with a decrease in pressure Decrease in pressure - favour reaction with an increase in pressure N2O4 (g)2NO2(g) (colourless)(brown)Click to view videoIncreasing Pressure Decreasing Pressure N2(g) + 3H2(g) 2NH3(g)( 4 vol/moles ) (2 vol/moles)Increasing Pressure Decreasing Pressure 11. Factors affecting the position of EquilibriumEffect of Pressure on the position of equilibriumIncrease in pressure - favour reaction with a decrease in pressure Decrease in pressure - favour reaction with an increase in pressure N2O4 (g)2NO2(g) (colourless) (brown) Click to view videoIncreasing Pressure Decreasing Pressure By reducing Volume By Increasing Volume Equilibrium shift to left Equilibrium shift to right Less molecules on left side More molecules on right sidePressure drops Pressure increase Formation of N2O4 (colourless) Formation of NO2 (brown)N2(g) + 3H2(g) 2NH3(g)( 4 vol/moles )(2 vol/moles)Increasing Pressure Decreasing Pressure Equilibrium shift to right Equilibrium shift to left Less molecules on left side More molecules on right sidePressure drops Pressure increase Formation of NH3 (product) Formation of H2 and N2 (reactants) 12. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established again Effect of Temperature on the position of equilibrium Increase in Temp Favours endothermic reaction Absorb heat to reduce Temp again Decrease in Temp Favours exothermic reaction Release heat to increase Temp again CoCl42- + 6H2O Co(H2O)62+ + 4CI H = -ve (exothermic)(blue) (pink)Click to view video Increase Temp Decrease Temp 13. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established again Effect of Temperature on the position of equilibrium Increase in Temp Favours endothermic reaction Absorb heat to reduce Temp again Decrease in Temp Favours exothermic reaction Release heat to increase Temp again CoCl42- + 6H2O Co(H2O)62+ + 4CI H = -ve (exothermic)(blue)(pink)Click to view video Increase Temp Decrease Temp By Heating it up By Cooling it down Favours endothermic reaction Favours exothermic reaction Equilibrium shift to left Equilibrium shift to right To reduce Temp To increase Temp Formation of CoCl42- (blue) Formation of Co(H2O)62+ (pink) Increase Temperature Rate of reaction increases Rate constant also changes Rate of forward and Rate of reverse increases but to different extend Position of equilibrium shift to endothermic to decrease Temp Kc, equilibrium constant change 14. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established again Effect of Temperature on the position of equilibrium Increase in Temp Favours endothermic reaction to absorb heat to reduce Temp again Decrease in Temp Favours exothermic reaction to release heat to increase Temp again N2O4 (g) 2NO2(g) H = + 54kJmol-1(colourless)(brown) Click to view video Increase Temp Decrease Temp 15. Factors affecting the position of EquilibriumLe Chateliers Principle A system in dynamic equilibrium is disturbed, the position of equilibrium will shift so as to cancel out the effect of change and a new equilibrium can be established again Effect of Temperature on the position of equilibrium Increase in Temp Favours endothermic reaction to absorb heat to reduce Temp again Decrease in Temp Favours exothermic reaction to release heat to increase Temp again N2O4 (g)2NO2(g) H = + 54kJmol-1(colourless)(brown) Click to view videoIncrease Temp Decrease Temp By Heating it up By Cooling it down Favours endothermic reaction Favours exothermic reaction Equilibrium shift to right Equilibrium shift to left To reduce Temp To increase Temp Formation of NO2 (brown) Formation of N2O4 (colourless) Increase Temperature Rate of reaction increases Rate constant also changes Rate of forward and Rate of reverse increases but to different extend Position of equilibrium shift to endothermic to decrease Temp Kc, equilibrium constant change 16. Factors affecting the position of EquilibriumEffect of Temperature on equilibrium constant, Kc Rate forward = kfA Rate reverse = krBH = +veArrhenius Equation show the relationship between temperature and rate constant Temperature will affect the rate constant for forward and reverseIncrease Temp equilibrium shift to right, endothermic side to decrease Temp - more product B producedRate of forward kf > Rate of reverse krKc = kf/kr or [conc product]/[conc reactant]Kc increase because ratio of kf/kr increase or ratio of product /reactant increase DecreaseTemp equilibrium shift to left - exothermic side to increase Temp - more reactant A producedRate of reverse kr > kfKc = kf/krKc decrease because ratio of kf/kr decrease or ratio of product /reactant decrease N2O4 (g)2NO2(g) H = + 54kJmol-1 For endothermic reaction Increase Temp - position equilibrium shift to right endothermic side to absorb heat Temp decrease Increase Temp forward rate, kf > reverse rate, kr - Kc = kf/kr = Kc increase Increase Temp - more product form, less reactants Kc = ratio of product/reactants Kc increases Conclusion : Endothermic Reaction Temp increase Kc increase Product increase 17. Factors affecting the position of EquilibriumEffect of Temperature on equilibrium constant, Kc Rate forward = kf A Rate reverse = kr B H = -veArrhenius Equation show the relationship between temperature and rate constant Temperature will affect the rate constant for forward and reverseIncrease Temp equilibrium shift to left, endothermic side to decrease Temp - more reactant A producedRate of reverse kr > Rate of forward kfKc = kf/kr or [conc product]/[conc reactant]Kc decrease because ratio of kf/kr decrease or ratio of product /reactant decrease DecreaseTemp equilibrium shift to right - exothermic side to increase Temp - more products B producedRate of forward kf > krKc = kf/krKc increase because ratio of kf/kr increase or ratio of product /reactant increase H2(g) + I2(g) 2HI(g) H = -9.6kJmol-1 For exothermic reaction Increase Temp - position equilibrium shift to left endothermic side to absorb heat Temp decrease Increase Temp reverse rate, kr > forward rate, kf - Kc = kf/kr = Kc decrease Increase Temp - more reactant form, less product Kc = ratio of product/reactants Kc decreases Conclusion : Exothermic Reaction Temp increase Kc decrease Product decrease 18. Factors affecting the position of EquilibriumEffect of Catalyst on equilibrium constant, KcCatalyst Provide an alternative pathway with lower activation energy Increase the rate of forward and reverse to the same extent/factor Position of equilibrium and Kc remains unchange Catalyst shorten the time it takes to reach equilibrium 19. Factors affecting the position of Equilibrium Effect of Catalyst on equilibrium constant, Kc Catalyst Provide an alternative pathway with lower activation energy Increase the rate of forward and reverse to the same extent/factor Position of equilibrium and Kc remains unchange Catalyst shorten the time it takes to reach equilibriumWithout catalyst, takes long reaching equilibrium With catalyst, reaching equilibrium fast 20. Factors affecting the position of Equilibrium Effect of Catalyst on equilibrium constant, Kc Catalyst Provide an alternative pathway with lower activation energy Increase the rate of forward and reverse to the same extent/factor Position of equilibrium and Kc remains unchange Catalyst shorten the time it takes to reach equilibriumWithout catalyst, takes long reaching equilibrium With catalyst, reaching equilibrium fastN2(g) + 3H2(g) 2NH3(g) H = - 92kJmol-1Effect of catalyst on Rate, Rate constant and Kc on ammonia productionAdding catalyst Rate increase Rate constant increase Equilibrium constant Kc No change Amount of product and reactants remainthe unchanged 21. Equilibrium LawWhen a reversible reaction achieved dynamic equilibrium - aA + bB cC and dD Equilibrium constant Kc = ratio of molar conc of product (raised to power of their respective stoichiometry coefficient) tomolar conc of reactants (raised to power of their respective stoichiometry coefficient) Kc is constant at constant temperatureaA + bB cC and dDKc = (C)c(D)d (A)a(B)bAt equilibrium:N2O4 (g) 2NO2 (g)N2O4 (g) 2NO2 (g)Rf (rate forward) = Rr (rate reverse)Kc = k f / k r Rf (rate forward) = Rr (rate reverse)kf [N2O4] = kr [NO2]2 kf [N2O4] = kr [NO2]2Kc = (NO2)2kf/kr = (NO2)2 (N2O4)(N2O4) Kc is a ratio of rate constant and is temperature dependent Kc is a ratio of products conc to reactants conc Magnitude of Kc indicate how far/extend of the reaction proceeds towards a product at a given temperature 22. Equilibrium LawWhen a reversible reaction achieved dynamic equilibrium - aA + bB cC and dD Equilibrium constant Kc = ratio of molar conc of product (raised to power of their respective stoichiometry coefficient) tomolar conc of reactants (raised to power of their respective stoichiometry coefficient) Kc is constant at constant temperatureaA + bB cC and dD Kc = (C)c(D)d(A)a(B)bAt equilibrium:N2O4 (g) 2NO2 (g)N2O4 (g) 2NO2 (g) Rf (rate forward) = Rr (rate reverse)Kc = k f / k rRf (rate forward) = Rr (rate reverse) kf [N2O4] = kr [NO2]2kf [N2O4] = kr [NO2]2 Kc = (NO2)2 kf/kr = (NO2)2(N2O4) (N2O4) Kc is a ratio of rate constant and is temperature dependent Kc is a ratio of products conc to reactants conc Magnitude of Kc indicate how far/extend of the reaction proceeds towards a product at a given temperatureSmall Kc :N2(g) + O2(g) 2NO(g) Kc = 1 x 10 -30 small Kc = (NO)2(N2)1(O2)1Kc small low product , more reactants , close to no reaction at allLarge Kc :2COg) + O2 2CO2(g) Kc = 2.2 x 10 22 high Kc = (CO2)2(CO)2(O2)1 Kc large high product , small reactants , close to completionIntermediate Kc :2HI(g) H2(g) + I2(g) Kc = 0.02 Kc = (H2)(I2) (HI)2 Kc intermediate significant amount of reactants and products 23. Equilibrium LawEffect of Concentration on equilibrium constant, Kc Increase in Conc - position of equilibrium shift to right/left - Conc will be Reduced Decrease in Conc position of equilibrium shift to right/left - Conc will be Increased Equilibrium Law applies to system at equilibrium Kc is constant at constant temperature Kc unaffected by Concentration, Pressure and Catalyst Addition of reactants and products will only shift position of equilibrium to right or left changing to a new equilibriumconcentration but Kc remains the same Magnitude of Kc indicate the extend or how far the reaction forms product/reactants but not how fast Kc High High product but rate can be very slow Kc Low Low product but rate can be very fast 24. Equilibrium LawEffect of Concentration on equilibrium constant, Kc Increase in Conc - position of equilibrium shift to right/left - Conc will be Reduced Decrease in Conc position of equilibrium shift to right/left - Conc will be Increased Equilibrium Law applies to system at equilibrium Kc is constant at constant temperature Kc unaffected by Concentration, Pressure and Catalyst Addition of reactants and products will only shift position of equilibrium to right or left changing to a new equilibriumconcentration but Kc remains the same Magnitude of Kc indicate the extend or how far the reaction forms product/reactants but not how fast Kc High High product but rate can be very slow Kc Low Low product but rate can be very fast Reaction between H2 + I2 2HIKc = 46.4 at 730K Kc = [HI]2 = 46.4[H2][I2]Initial ConcH2 + I2 2HIEquilibrium Conc 25. Equilibrium LawEffect of Concentration on equilibrium constant, Kc Increase in Conc - position of equilibrium shift to right/left - Conc will be Reduced Decrease in Conc position of equilibrium shift to right/left - Conc will be Increased Equilibrium Law applies to system at equilibrium Kc is constant at constant temperature Kc unaffected by Concentration, Pressure and Catalyst Addition of reactants and products will only shift position of equilibrium to right or left changing to a new equilibriumconcentration but Kc remains the same Magnitude of Kc indicate the extend or how far the reaction forms product/reactants but not how fast Kc High High product but rate can be very slow Kc Low Low product but rate can be very fast Reaction between H2 + I2 2HIKc = 46.4 at 730K Kc = [HI]2 = 46.4[H2][I2]Initial ConcH2 + I2 2HIEquilibrium ConcReaction contain different Initial Conc of H2 and I2 and HI but at equilibium Kc remains the same regardless of initial concKc = [HI]2 = 46.4[H2][I2] Kc unchanged 26. How dynamic equilibrium is shifted when H2 is added ? N2(g) + 3H2(g) 2NH3 (g) When more H2 added, position equilibrium will shift to right, to reduce the H2 conc and increase the NH3 conc Rate of forward and reverse will increase New equilibrium concentration will be achieved when rate of forward kf = rate of reverse kr More products NH3 and less reactants N2 but Kc value remains unchangedAt equilibriumRate forward kf = Rate reverse krKc = 4.07 27. How dynamic equilibrium is shifted when H2 is added ? N2(g) + 3H2(g) 2NH3 (g) When more H2 added, position equilibrium will shift to right, to reduce the H2 conc and increase the NH3 conc Rate of forward and reverse will increase New equilibrium concentration will be achieved when rate of forward kf = rate of reverse kr More products NH3 and less reactants N2 but Kc value remains unchanged H2 addedAt equilibriumEquilibrium shifted to rightRate forward kf = Rate reverse kr Rate forward kf > Rate reverse krKc = 4.07 Qc = 2.24 28. How dynamic equilibrium is shifted when H2 is added ? N2(g) + 3H2(g) 2NH3 (g) When more H2 added, position equilibrium will shift to right, to reduce the H2 conc and increase the NH3 conc Rate of forward and reverse will increase New equilibrium concentration will be achieved when rate of forward kf = rate of reverse kr More products NH3 and less reactants N2 but Kc value remains unchanged H2 addedNew equilibrium ConcAt equilibriumEquilibrium shifted to rightAt equilibrium againRate forward kf = Rate reverse kr Rate forward kf > Rate reverse kr Rate forward kf = Rate reverse krKc = 4.07 Qc = 2.24 Kc = 4.07 29. How dynamic equilibrium is shifted when H2 is added ? N2(g) + 3H2(g) 2NH3 (g) When more H2 added, position equilibrium will shift to right, to reduce the H2 conc and increase the NH3 conc Rate of forward and reverse will increase New equilibrium concentration will be achieved when rate of forward kf = rate of reverse kr More products NH3 and less reactants N2 but Kc value remains unchangedEquilibrium Conc for H2 = 0.82MEquilibrium Conc for N2 = 0.20MEquilibrium Conc for NH3 = 0.67MN2(g) + 3H2(g) 2NH3 (g) Kc = (NH3)2 (N2)(H2)3 Kc = (0.67)2(0.20)(0.82)3 Kc = 4.07 30. How dynamic equilibrium is shifted when H2 is added ? N2(g) + 3H2(g) 2NH3 (g) When more H2 added, position equilibrium will shift to right, to reduce the H2 conc and increase the NH3 conc Rate of forward and reverse will increase New equilibrium concentration will be achieved when rate of forward kf = rate of reverse kr More products NH3 and less reactants N2 but Kc value remains unchangedH2 addedEquilibrium Conc for H2 = 0.82MNew Conc for H2 = 1.00MEquilibrium Conc for N2 = 0.20MEquilibrium Conc for N2 = 0.20MEquilibrium Conc for NH3 = 0.67M Equilibrium Conc for NH3 = 0.67MN2(g) + 3H2(g) 2NH3 (g) N2(g) + 3H2(g) 2NH3 (g) Kc = (NH3)2 Qc = (NH3)2 (N2)(H2)3 (N2)(H2)3 Kc = (0.67)2 Qc = (0.67)2(0.20)(0.82)3 (0.20)(1.00)3 Kc = 4.07 Qc = 2.24 31. How dynamic equilibrium is shifted when H2 is added ? N2(g) + 3H2(g) 2NH3 (g) When more H2 added, position equilibrium will shift to right, to reduce the H2 conc and increase the NH3 conc Rate of forward and reverse will increase New equilibrium concentration will be achieved when rate of forward kf = rate of reverse kr More products NH3 and less reactants N2 but Kc value remains unchangedH2 addedNew equilibrium ConcEquilibrium Conc for H2 = 0.82MNew Conc for H2 = 1.00MNew Equilibrium Conc for H2 = 0.90MEquilibrium Conc for N2 = 0.20MEquilibrium Conc for N2 = 0.20MNew Equilibrium Conc for N2 = 0.19MEquilibrium Conc for NH3 = 0.67M Equilibrium Conc for NH3 = 0.67M New Equilibrium Conc for NH3 = 0.75MN2(g) + 3H2(g) 2NH3 (g) N2(g) + 3H2(g) 2NH3 (g)N2(g) + 3H2(g) 2NH3 (g) Kc = (NH3)2 Qc = (NH3)2 Kc = (NH3)2 (N2)(H2)3 (N2)(H2)3(N2)(H2)3 Kc = (0.67)2 Qc = (0.67)2 Kc = (0.75)2(0.20)(0.82)3 (0.20)(1.00)3 (0.19)(0.90)3 Kc = 4.07 Qc = 2.24 Qc < Kc Kc = 4.072.24 < 4.07 Kc must remain constant Shift to the right Increase products and decrease reactants New equilibrium Conc is achieved Qc = Kc again 32. AcknowledgementsThanks to source of pictures and video used in this presentationThanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/Prepared by Lawrence KokCheck out more video tutorials from my site and hope you enjoy this tutorialhttp://lawrencekok.blogspot.com