1. Tutorial on Rate Law, RateExpression, Order of Reaction, Initial Rateand Half Life . Prepared by Lawrence Kok http://lawrencekok.blogspot.com

2. Reaction Rates / Kinetics During chemical reaction, reactants are consumed, products are formed Amount of reactants decreases , Amount of products increases Rate of reaction follows stoichiometric principlesReaction A B For every ONE A breakdown = ONE B will form d [ A] d [ B] Rate of decomposition A = Rate of formation of B dt dt2NO 2 N2O4 H 2 + I2 2HI1d [ N 02] 1d [ N 204] 1d [ H 2]1d [ I 2] d [ HI ] 2dtdtdt dt 2dt 3. Reaction Rates / Kinetics During chemical reaction, reactants are consumed, products are formed Amount of reactants decreases , Amount of products increases Rate of reaction follows stoichiometric principlesReaction A B For every ONE A breakdown = ONE B will form d [ A]d [ B] Rate of decomposition A = Rate of formation of B dtdt2NO 2 N2O4 H 2 + I2 2HI 1d [ N 02] 1d [ N 204]1d [ H 2] 1d [ I 2] d [ HI ]2dtdt dtdt 2dt Two moles NO2 decompose = One mole of N2O4 form One mole H2 decompose = TWO moles of HI form NO2 used up is twice as fast as N2O4 produced Rate of H2 and I2 decomposition are the same but only half the rate of HI formation 4. Rate of reaction can be defined as a change of property over timeX Y(Reactants) (Products) X decrease over time Y increase over time X consumed X formed Rate of Decrease of XRate of Increase of Y Decrease Concentration X /time Increase Concentration Y /time Decrease Volume X /Time Increase Volume Y /Time Decrease Absorbance X /Time Increase Absorbance Y /Time 5. Graphical Representation of Order of reactions, ZERO, FIRST and SECOND order ZERO ORDER FIRST ORDERSECOND ORDER Conc double x2 Rate constant Conc double x2 Rate double x2 Conc double x2 Rate quadruple x 4 Rate Vs Conc Constant Rate triple x3 Rate triple x3 Rate triple x3 Rate increase x 9 Conc Vs Time Linear Conc Vs Time Linear Rate = k[A]0 Rate = k[A]1 Rate = k[A]2 Rate is independent of [A] Rate - 1st order respect to [A]Rate - 2nd order respect to [A]Unit for k (rate constant) Unit for k (rate constant)Unit for k (rate constant)Rate = k[A]0 Rate = k[A]1Rate = k[A]2Rate = k Rate = kA Rate = kA2 k = Ms-1 k = s-1 k = M-1s-1 6. Graphical Representation of Half Life for ZERO, FIRST and SECOND orderZERO ORDER FIRST ORDERSECOND ORDER 7. Graphical Representation of Half Life for ZERO, FIRST and SECOND orderZERO ORDER FIRST ORDERSECOND ORDER 1 1/2 1/4 1/8 1 1/2 1/4 1/8 1 1/2 1/4 1/810m5m2.5m 10m 10m10m 10m 20m40mHalf Life is directly proportional to Conc Half Life is independent of Conc (constant) Half Life is inversely proportional to Conc 8. Reaction Law / Rate ExpressionFor a reaction: aA + bB cC + dD Stoichiometry equation : Shows the mole ratio of reactants and products Rate equation: Equation relates rate of reaction with concentration of reactants : How concentration of reactants affect the rateReaction equation = k[A]x[B]yx = rate order with respect to [A] y = rate order with respect to [B] (x +y) = overall orderk = rate constantRate order must be determined experimentally , NOT derived from stoichiometry coefficientsGraphical Representation of Order of reactions, ZERO, FIRST and SECOND order 9. Order of reaction can be determined using THREE methods Initial Rate methodConc Vs Time Method Conc Vs Time Method(Multiple Single Runs) (Half Life)(Whole Curve/Tangent Method) Monitoring the decrease in Monitoring the decrease in Multiple Single RunsConc of a single reactants Conc of a single reactants Varying and Keeping Using Half Life to determine Using gradients of tangentscertain Conc fixed Wasteful as multiple the orderat different reactant conc runs needed 10. Order of reaction can be determined using THREE methods Initial Rate methodConc Vs Time MethodConc Vs Time Method(Multiple Single Runs) (Half Life) (Whole Curve/Tangent Method) Monitoring the decrease in Monitoring the decrease in Multiple Single Runs Conc of a single reactantsConc of a single reactants Varying and Keeping Using Half Life to determine Using gradients of tangentscertain Conc fixed Wasteful as multiplethe order at different reactant conc runs needed Zero order Half Life is directly proportional to Conc Conc x2 rate x2 - 1st order1st order Conc x2 rate x4 2nd order Convert Conc Vs Time to Rate vs Conc Conc x2 rate x0 zero order Half Life is independent of Conc (constant) 2nd order Initial Rate is taken at time O by Rate Vs Conc straight line 1st Order drawing a tangent at time OHalf Life is inversely proportional to Conc 11. Using Conc Vs Time and Conc Vs Rate Method to determine Order of reactionReaction between 2A B + CPlot a graph of Conc A Vs Time to determine the order, initial rate and rate constant, kReaction between 2N205 4N02 + 02Plot a graph of Rate Vs Conc to determine the order and rate constant, k 12. Using Conc Vs Time and Conc Vs Rate Method to determine Order of reactionReaction between 2A B + CPlot a graph of Conc A Vs Time to determine the order, initial rate and rate constant, kConc Vs Time Method Half Life for A is constant = 80s 1st order respect to [A] Formula for 1st order half life t1/2 = 0.693/k = 0.693/80 = 8.66 x 10-3 s-1Reaction between 2N205 4N02 + 02Plot a graph of Rate Vs Conc to determine the order and rate constant, kConc Vs Rate Method Straight Line 1st order respect to [N205] Rate = k[N205 ], k = gradient = 7.86 x 10-6 s-1 13. Using Initial rate and Half Life to determine order of reactionReaction on hydrolysis of ester by OH- given by Ester + OH- X + YReaction was done using two different OH- concentrationRun 1 [OH- ] 0.20M Run 2 [OH- ] 0.40MConc ester Vs Time was plotted. Determine the order and initial rate of reactionDetermine rate order for OH- (fix conc ester) Determine rate order for ester (Using Half Life )Calculate rate constant, k 14. Using Initial rate and Half Life to determine order of reaction Reaction on hydrolysis of ester by OH- given by Ester + OH- X + Y Reaction was done using two different OH- concentration Run 1 [OH- ] 0.20M Run 2 [OH- ] 0.40M Conc ester Vs Time was plotted. Determine the order and initial rate of reaction Determine rate order for OH- (fix conc ester)Determine rate order for ester (Using Half Life ) Let Rate = k[OH-]x [ester] y Using run 2 : Conc ester vs TimeHalf Life for Ester t1/2 = 11.5min (constant)1st order with respect to ester 1st order with respect to OH -Calculate rate constant, k Rate = k[OH-]1 [ester]1 Half life : 0.001 0.0005 0.00025 is (11.5min)For run 2 : Initial Rate Run 1 Gradient at time 0 = (0.006 0.0006)/(10-0) Initial rate = 8.00 x10-5, [OH-]= 0.4M, [ester] = 0.001M = 4.00 x 10-5 Rate = k[OH-]1 [ester]1 Initial Rate Run 2 Gradient time 0 = (0.001 0.0002)/(10-0) 8.00 x 10-5 = k[0.4]1[0.001]1 = k = 0.200M-1min-1 = 8.00x10-5 15. Using Initial rate and Half Life to determine order of reaction Reaction between RBr + OH- ROH + Br- Reaction was done using TWO different OH- concentration Run 1 [OH- ] 0.10MRun 2 [OH- ] 0.15M Conc RBr Vs Time was plotted. Determine the order and initial rate of reaction Determine rate order for OH- (fix conc RBr) Determine rate order for RBr (using half life)Calculate rate constant, k 16. Using Initial rate and Half Life to determine order of reaction Reaction between RBr + OH- ROH + Br- Reaction was done using TWO different OH- concentration Run 1 [OH- ] 0.10MRun 2 [OH- ] 0.15M Conc RBr Vs Time was plotted. Determine the order and initial rate of reaction Determine rate order for OH- (fix conc RBr) Let Rate = k[OH-]x [RBr] y Determine rate order for RBr (using half life) Using run 2 : Conc vs Time Half Life for RBr t1/2 = 78min (constant) 1st order with respect to RBr Half life : 0.01 0.005 0.0025 Initial Rate Run 1 Gradient time 0 = 5.25 x10-5 1st order with respect to OH -Initial Rate Run 2 Gradient time 0 = 8.00 x10-5Calculate rate constant, k 17. Using Initial rate and Half Life to determine order of reactionReaction between RBr + OH- ROH + Br-Reaction was done using TWO different OH- concentrationRun 1 [OH- ] 0.10MRun 2 [OH- ] 0.15MConc RBr Vs Time was plotted. Determine the order and initial rate of reactionDetermine rate order for OH- (fix conc RBr)Let Rate = k[OH-]x [RBr] yDetermine rate order for RBr (using half life)Using run 2 : Conc vs TimeHalf Life for RBr t1/2 = 78min (constant)1st order with respect to RBrHalf life : 0.01 0.005 0.0025Initial Rate Run 1 Gradient time 0 = 5.25 x10-51st order with respect to OH -Initial Rate Run 2 Gradient time 0 = 8.00 x10-5Calculate rate constant, k Rate = k[OH-]1 [RBr]1 Rate = k[OH-]1 [RBr]1 For run 1 : Initial rate = 5.25 x10-5, [OH-] = 0.10M, [RBr] = 0.01M Rate = k[OH-]1 [RBr]1 5.25 x10-5 = k[0.10]1[0.01]1 = k = 0.0525M-1min-1 18. Using Initial rate and Half Life to determine order of reactionReaction between CH3CO2C2H5 + H2O CH3CO2H + C2H5OHReaction was done using TWO different HCI concentrationRun 1 [HCI] 0.10M Run 2 [HCI ] 0.20MConc CH3CO2C2H5 Vs Time was plotted. Determine the order and initial rate of reactionDetermine rate order for HCI (fix conc CH3CO2C2H5 ) Determine rate order for CH3CO2C2H5 (using half life) 19. Using Initial rate and Half Life to determine order of reactionReaction between CH3CO2C2H5 + H2O CH3CO2H + C2H5OHReaction was done using TWO different HCI concentrationRun 1 [HCI] 0.10M Run 2 [HCI ] 0.20MConc CH3CO2C2H5 Vs Time was plotted. Determine the order and initial rate of reactionDetermine rate order for HCI (fix conc CH3CO2C2H5 ) Determine rate order for CH3CO2C2H5 (using half life)Let Rate = k[HCI]x [CH3CO2C2H5] y Half life for run 2 -> 0.200 0.100 0.050Half Life for CH3CO2C2H5 t1/2 = 31min (constant)1st order with respect to CH3CO2C2H5Half life is 31min (constant)Initial rate Run 1 Gradient time 0 = 1.90 x10-3Initial rate Run 2 Gradient time 0 = 3.80 x10-31st order with respect to HCI 20. Using Initial rate and Half Life to determine order of reactionReaction between CH3CO2C2H5 + H2O CH3CO2H + C2H5OHReaction was done using TWO different HCI concentrationRun 1 [HCI] 0.10M Run 2 [HCI ] 0.20MConc CH3CO2C2H5 Vs Time was plotted. Determine the order and initial rate of reactionDetermine rate order for HCI (fix conc CH3CO2C2H5 ) Determine rate order for CH3CO2C2H5 (using half life)Let Rate = k[HCI]x [CH3CO2C2H5] y Half life for run 2 -> 0.200 0.100 0.050Half Life for CH3CO2C2H5 t1/2 = 31min (constant)1st order with respect to CH3CO2C2H5Half life is 31min (constant)Initial rate Run 1 Gradient time 0 = 1.90 x10-3Initial rate Run 2 Gradient time 0 = 3.80 x10-31st order with respect to HCIRate = k[HCI]1[CH3CO2C2H5]1 21. Using Initial Rate Method to determine Order of reaction Reaction between A + B ABEx 1Determine rate order for A (fix conc B )Determine rate order for B (fix conc A ) 22. Using Initial Rate Method to determine Order of reactionReaction between A + B ABEx 1Determine rate order for A (fix conc B )Determine rate order for B (fix conc A )Let Rate = k[A]x[B] y Let Rate = k[A]x[B] y2nd order with respect to A 1st order with respect to B Rate = k[A]2[B]1 23. Using Initial Rate Method to determine Order of reaction Reaction between F2 + 2CIO2 2FCIO2Ex 2Determine rate order for CIO2 (fix conc F2 ) Determine rate order for F2 (fix conc CIO2)To calculate k 24. Using Initial Rate Method to determine Order of reactionReaction between F2 + 2CIO2 2FCIO2 Ex 2Determine rate order for CIO2 (fix conc F2 )Determine rate order for F2 (fix conc CIO2)Let Rate = k[F2]x [CIO2] yLet Rate = k[F2]x [CIO2] y 1st order with respect to F2 1st order with respect to CIO2To calculate k 25. Using Initial Rate Method to determine Order of reaction Reaction between F2 + 2CIO2 2FCIO2Ex 2 Determine rate order for CIO2 (fix conc F2 ) Determine rate order for F2 (fix conc CIO2) Let Rate = k[F2]x [CIO2] y Let Rate = k[F2]x [CIO2] y 1st order with respect to F21st order with respect to CIO2To calculate k Rate = k [CIO2] 1[F2]1For expt 1 : Initial rate = 1.2 x 10-3 , [F2] = 0.10M, [CIO2] = 0.01MRate = k[F2]1[CIO2]11.2 x 10-3 = k[0.10]1[0.01]1, k = 1.2M-1s-1 26. Using Initial Rate Method to determine Order of reactionReaction between 2CIO2 + 2OH- CIO3- + CIO2- + H2O Ex 3Determine rate order for CIO2 (fix conc OH- ) Determine rate order for OH- (fix conc CIO2 )To calculate k 27. Using Initial Rate Method to determine Order of reaction Reaction between 2CIO2 + 2OH- CIO3- + CIO2- + H2OEx 3Determine rate order for CIO2 (fix conc OH- )Determine rate order for OH- (fix conc CIO2 )Let Rate = k[CIO2]x[OH-]yLet Rate = k[CIO2]x[OH-]y 1st order with respect to OH- 2nd order with respect to CIO2To calculate k 28. Using Initial Rate Method to determine Order of reaction Reaction between 2CIO2 + 2OH- CIO3- + CIO2- + H2OEx 3Determine rate order for CIO2 (fix conc OH- )Determine rate order for OH- (fix conc CIO2 )Let Rate = k[CIO2]x[OH-]yLet Rate = k[CIO2]x[OH-]y1st order with respect to OH- 2nd order with respect to CIO2 To calculate k Rate = k[CIO2]2[OH-] 1For expt 1 : Initial rate = 8.00 x 10-3 , [CIO2] = 0.025M, [OH-] = 0.046MRate = k[CIO2]2[OH-] 18.00 x 10-3 = k[0.025]1[0.046]1, k = 278.3M-1s-1 29. Using Initial Rate Method to determine Order of reaction Reaction between Br2 + 2NO 2NOBrEx 4Determine rate order for Br2 (fix conc NO ) Determine rate order for NO (fix conc Br2 )To calculate initial rate whenTo calculate k0.1M Br2 and 0.3M NO are used 30. Using Initial Rate Method to determine Order of reaction Reaction between Br2 + 2NO 2NOBr Ex 4Determine rate order for Br2 (fix conc NO )Determine rate order for NO (fix conc Br2 )Let Rate = k[Br2]x[NO]yLet Rate = k[Br2]x[NO]y 1st order with respect to Br2 2nd order with respect to NOTo calculate initial rate whenTo calculate k0.1M Br2 and 0.3M NO are used 31. Using Initial Rate Method to determine Order of reaction Reaction between Br2 + 2NO 2NOBr Ex 4Determine rate order for Br2 (fix conc NO ) Determine rate order for NO (fix conc Br2 )Let Rate = k[Br2]x[NO]y Let Rate = k[Br2]x[NO]y 1st order with respect to Br22nd order with respect to NOTo calculate k Rate = k[Br2]1[NO]2 To calculate initial rate when 0.1M Br2 and 0.3M NO are usedFor expt 1 : Initial rate = 12Ms-1, [Br2] = 0.10M, [NO] = 0.10M Rate = k[Br2]1[NO]2Rate = k[Br2]1[NO]2 Rate = 12,000 x 0.1 x 0.1 212 = k[0.10]1[0.10]2 , k = 12,000M-1min-1 Rate = 108Ms-1 32. Questions on Reaction Rates / KineticsEX 5 2H2 + 02 2H20 When rate of O2 decrease is at 0.23Ms-1, what is the rate of H2O formation/ increases EX 6 C3H8 + 5O2 3C02 + 4H2O When rate of C3H8 decrease is at 0.30Ms-1, what is the rate of 02 decrease 33. Questions on Reaction Rates / KineticsEX 5 2H2 + 02 2H20 When rate of O2 decrease is at 0.23Ms-1, what is the rate of H2O formation/ increases EX 6 C3H8 + 5O2 3C02 + 4H2O When rate of C3H8 decrease is at 0.30Ms-1, what is the rate of 02 decrease 34. 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