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3305-3308
3 6 Time required to decompose SO2Cl2 to half of its initial amount is 60 minutes If the decomposition is a first order reaction, calculate the rate constant of the reaction Rationalised 2023-24 79 Chemical Kinetics k = A e -Ea /RT (3
1
3306-3309
6 Time required to decompose SO2Cl2 to half of its initial amount is 60 minutes If the decomposition is a first order reaction, calculate the rate constant of the reaction Rationalised 2023-24 79 Chemical Kinetics k = A e -Ea /RT (3 18) where A is the Arrhenius factor or the frequency factor
1
3307-3310
If the decomposition is a first order reaction, calculate the rate constant of the reaction Rationalised 2023-24 79 Chemical Kinetics k = A e -Ea /RT (3 18) where A is the Arrhenius factor or the frequency factor It is also called pre-exponential factor
1
3308-3311
Rationalised 2023-24 79 Chemical Kinetics k = A e -Ea /RT (3 18) where A is the Arrhenius factor or the frequency factor It is also called pre-exponential factor It is a constant specific to a particular reaction
1
3309-3312
18) where A is the Arrhenius factor or the frequency factor It is also called pre-exponential factor It is a constant specific to a particular reaction R is gas constant and Ea is activation energy measured in joules/mole (J mol –1)
1
3310-3313
It is also called pre-exponential factor It is a constant specific to a particular reaction R is gas constant and Ea is activation energy measured in joules/mole (J mol –1) It can be understood clearly using the following simple reaction       2 2 H g I g 2HI g   According to Arrhenius, this reaction can take place only when a molecule of hydrogen and a molecule of iodine collide to form an unstable intermediate (Fig
1
3311-3314
It is a constant specific to a particular reaction R is gas constant and Ea is activation energy measured in joules/mole (J mol –1) It can be understood clearly using the following simple reaction       2 2 H g I g 2HI g   According to Arrhenius, this reaction can take place only when a molecule of hydrogen and a molecule of iodine collide to form an unstable intermediate (Fig 3
1
3312-3315
R is gas constant and Ea is activation energy measured in joules/mole (J mol –1) It can be understood clearly using the following simple reaction       2 2 H g I g 2HI g   According to Arrhenius, this reaction can take place only when a molecule of hydrogen and a molecule of iodine collide to form an unstable intermediate (Fig 3 6)
1
3313-3316
It can be understood clearly using the following simple reaction       2 2 H g I g 2HI g   According to Arrhenius, this reaction can take place only when a molecule of hydrogen and a molecule of iodine collide to form an unstable intermediate (Fig 3 6) It exists for a very short time and then breaks up to form two molecules of hydrogen iodide
1
3314-3317
3 6) It exists for a very short time and then breaks up to form two molecules of hydrogen iodide Fig
1
3315-3318
6) It exists for a very short time and then breaks up to form two molecules of hydrogen iodide Fig 3
1
3316-3319
It exists for a very short time and then breaks up to form two molecules of hydrogen iodide Fig 3 6: Formation of HI through the intermediate Intermediate Fig
1
3317-3320
Fig 3 6: Formation of HI through the intermediate Intermediate Fig 3
1
3318-3321
3 6: Formation of HI through the intermediate Intermediate Fig 3 7: Diagram showing plot of potential energy vs reaction coordinate Fig
1
3319-3322
6: Formation of HI through the intermediate Intermediate Fig 3 7: Diagram showing plot of potential energy vs reaction coordinate Fig 3
1
3320-3323
3 7: Diagram showing plot of potential energy vs reaction coordinate Fig 3 8: Distribution curve showing energies among gaseous molecules The energy required to form this intermediate, called activated complex (C), is known as activation energy (Ea)
1
3321-3324
7: Diagram showing plot of potential energy vs reaction coordinate Fig 3 8: Distribution curve showing energies among gaseous molecules The energy required to form this intermediate, called activated complex (C), is known as activation energy (Ea) Fig
1
3322-3325
3 8: Distribution curve showing energies among gaseous molecules The energy required to form this intermediate, called activated complex (C), is known as activation energy (Ea) Fig 3
1
3323-3326
8: Distribution curve showing energies among gaseous molecules The energy required to form this intermediate, called activated complex (C), is known as activation energy (Ea) Fig 3 7 is obtained by plotting potential energy vs reaction coordinate
1
3324-3327
Fig 3 7 is obtained by plotting potential energy vs reaction coordinate Reaction coordinate represents the profile of energy change when reactants change into products
1
3325-3328
3 7 is obtained by plotting potential energy vs reaction coordinate Reaction coordinate represents the profile of energy change when reactants change into products Some energy is released when the complex decomposes to form products
1
3326-3329
7 is obtained by plotting potential energy vs reaction coordinate Reaction coordinate represents the profile of energy change when reactants change into products Some energy is released when the complex decomposes to form products So, the final enthalpy of the reaction depends upon the nature of reactants and products
1
3327-3330
Reaction coordinate represents the profile of energy change when reactants change into products Some energy is released when the complex decomposes to form products So, the final enthalpy of the reaction depends upon the nature of reactants and products All the molecules in the reacting species do not have the same kinetic energy
1
3328-3331
Some energy is released when the complex decomposes to form products So, the final enthalpy of the reaction depends upon the nature of reactants and products All the molecules in the reacting species do not have the same kinetic energy Since it is difficult to predict the behaviour of any one molecule with precision, Ludwig Boltzmann and James Clark Maxwell used statistics to predict the behaviour of large number of molecules
1
3329-3332
So, the final enthalpy of the reaction depends upon the nature of reactants and products All the molecules in the reacting species do not have the same kinetic energy Since it is difficult to predict the behaviour of any one molecule with precision, Ludwig Boltzmann and James Clark Maxwell used statistics to predict the behaviour of large number of molecules According to them, the distribution of kinetic energy may be described by plotting the fraction of molecules (NE/NT) with a given kinetic energy (E) vs kinetic energy (Fig
1
3330-3333
All the molecules in the reacting species do not have the same kinetic energy Since it is difficult to predict the behaviour of any one molecule with precision, Ludwig Boltzmann and James Clark Maxwell used statistics to predict the behaviour of large number of molecules According to them, the distribution of kinetic energy may be described by plotting the fraction of molecules (NE/NT) with a given kinetic energy (E) vs kinetic energy (Fig 3
1
3331-3334
Since it is difficult to predict the behaviour of any one molecule with precision, Ludwig Boltzmann and James Clark Maxwell used statistics to predict the behaviour of large number of molecules According to them, the distribution of kinetic energy may be described by plotting the fraction of molecules (NE/NT) with a given kinetic energy (E) vs kinetic energy (Fig 3 8)
1
3332-3335
According to them, the distribution of kinetic energy may be described by plotting the fraction of molecules (NE/NT) with a given kinetic energy (E) vs kinetic energy (Fig 3 8) Here, NE is the number of molecules with energy E and NT is total number of molecules
1
3333-3336
3 8) Here, NE is the number of molecules with energy E and NT is total number of molecules The peak of the curve corresponds to the most probable kinetic energy, i
1
3334-3337
8) Here, NE is the number of molecules with energy E and NT is total number of molecules The peak of the curve corresponds to the most probable kinetic energy, i e
1
3335-3338
Here, NE is the number of molecules with energy E and NT is total number of molecules The peak of the curve corresponds to the most probable kinetic energy, i e , kinetic energy of maximum fraction of molecules
1
3336-3339
The peak of the curve corresponds to the most probable kinetic energy, i e , kinetic energy of maximum fraction of molecules There are decreasing number of molecules with energies higher or lower than this value
1
3337-3340
e , kinetic energy of maximum fraction of molecules There are decreasing number of molecules with energies higher or lower than this value When the Rationalised 2023-24 80 Chemistry Fig
1
3338-3341
, kinetic energy of maximum fraction of molecules There are decreasing number of molecules with energies higher or lower than this value When the Rationalised 2023-24 80 Chemistry Fig 3
1
3339-3342
There are decreasing number of molecules with energies higher or lower than this value When the Rationalised 2023-24 80 Chemistry Fig 3 10: A plot between ln k and 1/T In Fig
1
3340-3343
When the Rationalised 2023-24 80 Chemistry Fig 3 10: A plot between ln k and 1/T In Fig 3
1
3341-3344
3 10: A plot between ln k and 1/T In Fig 3 10, slope = – Ea R and intercept = ln A
1
3342-3345
10: A plot between ln k and 1/T In Fig 3 10, slope = – Ea R and intercept = ln A So we can calculate Ea and A using these values
1
3343-3346
3 10, slope = – Ea R and intercept = ln A So we can calculate Ea and A using these values At temperature T1, equation (3
1
3344-3347
10, slope = – Ea R and intercept = ln A So we can calculate Ea and A using these values At temperature T1, equation (3 19) is ln k1 = – a 1 E RT + ln A (3
1
3345-3348
So we can calculate Ea and A using these values At temperature T1, equation (3 19) is ln k1 = – a 1 E RT + ln A (3 20) At temperature T2, equation (3
1
3346-3349
At temperature T1, equation (3 19) is ln k1 = – a 1 E RT + ln A (3 20) At temperature T2, equation (3 19) is ln k2 = – a 2 E RT + ln A (3
1
3347-3350
19) is ln k1 = – a 1 E RT + ln A (3 20) At temperature T2, equation (3 19) is ln k2 = – a 2 E RT + ln A (3 21) (since A is constant for a given reaction) k1 and k2 are the values of rate constants at temperatures T1 and T2 respectively
1
3348-3351
20) At temperature T2, equation (3 19) is ln k2 = – a 2 E RT + ln A (3 21) (since A is constant for a given reaction) k1 and k2 are the values of rate constants at temperatures T1 and T2 respectively Fig
1
3349-3352
19) is ln k2 = – a 2 E RT + ln A (3 21) (since A is constant for a given reaction) k1 and k2 are the values of rate constants at temperatures T1 and T2 respectively Fig 3
1
3350-3353
21) (since A is constant for a given reaction) k1 and k2 are the values of rate constants at temperatures T1 and T2 respectively Fig 3 9: Distribution curve showing temperature dependence of rate of a reaction temperature is raised, the maximum of the curve moves to the higher energy value (Fig
1
3351-3354
Fig 3 9: Distribution curve showing temperature dependence of rate of a reaction temperature is raised, the maximum of the curve moves to the higher energy value (Fig 3
1
3352-3355
3 9: Distribution curve showing temperature dependence of rate of a reaction temperature is raised, the maximum of the curve moves to the higher energy value (Fig 3 9) and the curve broadens out, i
1
3353-3356
9: Distribution curve showing temperature dependence of rate of a reaction temperature is raised, the maximum of the curve moves to the higher energy value (Fig 3 9) and the curve broadens out, i e
1
3354-3357
3 9) and the curve broadens out, i e , spreads to the right such that there is a greater proportion of molecules with much higher energies
1
3355-3358
9) and the curve broadens out, i e , spreads to the right such that there is a greater proportion of molecules with much higher energies The area under the curve must be constant since total probability must be one at all times
1
3356-3359
e , spreads to the right such that there is a greater proportion of molecules with much higher energies The area under the curve must be constant since total probability must be one at all times We can mark the position of Ea on Maxwell Boltzmann distribution curve (Fig
1
3357-3360
, spreads to the right such that there is a greater proportion of molecules with much higher energies The area under the curve must be constant since total probability must be one at all times We can mark the position of Ea on Maxwell Boltzmann distribution curve (Fig 3
1
3358-3361
The area under the curve must be constant since total probability must be one at all times We can mark the position of Ea on Maxwell Boltzmann distribution curve (Fig 3 9)
1
3359-3362
We can mark the position of Ea on Maxwell Boltzmann distribution curve (Fig 3 9) Increasing the temperature of the substance increases the fraction of molecules, which collide with energies greater than Ea
1
3360-3363
3 9) Increasing the temperature of the substance increases the fraction of molecules, which collide with energies greater than Ea It is clear from the diagram that in the curve at (t + 10), the area showing the fraction of molecules having energy equal to or greater than activation energy gets doubled leading to doubling the rate of a reaction
1
3361-3364
9) Increasing the temperature of the substance increases the fraction of molecules, which collide with energies greater than Ea It is clear from the diagram that in the curve at (t + 10), the area showing the fraction of molecules having energy equal to or greater than activation energy gets doubled leading to doubling the rate of a reaction In the Arrhenius equation (3
1
3362-3365
Increasing the temperature of the substance increases the fraction of molecules, which collide with energies greater than Ea It is clear from the diagram that in the curve at (t + 10), the area showing the fraction of molecules having energy equal to or greater than activation energy gets doubled leading to doubling the rate of a reaction In the Arrhenius equation (3 18) the factor e -Ea /RT corresponds to the fraction of molecules that have kinetic energy greater than Ea
1
3363-3366
It is clear from the diagram that in the curve at (t + 10), the area showing the fraction of molecules having energy equal to or greater than activation energy gets doubled leading to doubling the rate of a reaction In the Arrhenius equation (3 18) the factor e -Ea /RT corresponds to the fraction of molecules that have kinetic energy greater than Ea Taking natural logarithm of both sides of equation (3
1
3364-3367
In the Arrhenius equation (3 18) the factor e -Ea /RT corresponds to the fraction of molecules that have kinetic energy greater than Ea Taking natural logarithm of both sides of equation (3 18) ln k = – Ea RT + ln A (3
1
3365-3368
18) the factor e -Ea /RT corresponds to the fraction of molecules that have kinetic energy greater than Ea Taking natural logarithm of both sides of equation (3 18) ln k = – Ea RT + ln A (3 19) The plot of ln k vs 1/T gives a straight line according to the equation (3
1
3366-3369
Taking natural logarithm of both sides of equation (3 18) ln k = – Ea RT + ln A (3 19) The plot of ln k vs 1/T gives a straight line according to the equation (3 19) as shown in Fig
1
3367-3370
18) ln k = – Ea RT + ln A (3 19) The plot of ln k vs 1/T gives a straight line according to the equation (3 19) as shown in Fig 3
1
3368-3371
19) The plot of ln k vs 1/T gives a straight line according to the equation (3 19) as shown in Fig 3 10
1
3369-3372
19) as shown in Fig 3 10 Thus, it has been found from Arrhenius equation (3
1
3370-3373
3 10 Thus, it has been found from Arrhenius equation (3 18) that increasing the temperature or decreasing the activation energy will result in an increase in the rate of the reaction and an exponential increase in the rate constant
1
3371-3374
10 Thus, it has been found from Arrhenius equation (3 18) that increasing the temperature or decreasing the activation energy will result in an increase in the rate of the reaction and an exponential increase in the rate constant Rationalised 2023-24 81 Chemical Kinetics The rate constants of a reaction at 500K and 700K are 0
1
3372-3375
Thus, it has been found from Arrhenius equation (3 18) that increasing the temperature or decreasing the activation energy will result in an increase in the rate of the reaction and an exponential increase in the rate constant Rationalised 2023-24 81 Chemical Kinetics The rate constants of a reaction at 500K and 700K are 0 02s–1 and 0
1
3373-3376
18) that increasing the temperature or decreasing the activation energy will result in an increase in the rate of the reaction and an exponential increase in the rate constant Rationalised 2023-24 81 Chemical Kinetics The rate constants of a reaction at 500K and 700K are 0 02s–1 and 0 07s–1 respectively
1
3374-3377
Rationalised 2023-24 81 Chemical Kinetics The rate constants of a reaction at 500K and 700K are 0 02s–1 and 0 07s–1 respectively Calculate the values of Ea and A
1
3375-3378
02s–1 and 0 07s–1 respectively Calculate the values of Ea and A 2 1 log k k = 2 1 a 1 2 2
1
3376-3379
07s–1 respectively Calculate the values of Ea and A 2 1 log k k = 2 1 a 1 2 2 303 T T E T T R        0
1
3377-3380
Calculate the values of Ea and A 2 1 log k k = 2 1 a 1 2 2 303 T T E T T R        0 07 log 0
1
3378-3381
2 1 log k k = 2 1 a 1 2 2 303 T T E T T R        0 07 log 0 02 = a 1 1 700 500 2
1
3379-3382
303 T T E T T R        0 07 log 0 02 = a 1 1 700 500 2 303 8
1
3380-3383
07 log 0 02 = a 1 1 700 500 2 303 8 314 J mol 700 500 E K                  0
1
3381-3384
02 = a 1 1 700 500 2 303 8 314 J mol 700 500 E K                  0 544 = Ea × 5
1
3382-3385
303 8 314 J mol 700 500 E K                  0 544 = Ea × 5 714 × 10-4/19
1
3383-3386
314 J mol 700 500 E K                  0 544 = Ea × 5 714 × 10-4/19 15 Ea = 0
1
3384-3387
544 = Ea × 5 714 × 10-4/19 15 Ea = 0 544 × 19
1
3385-3388
714 × 10-4/19 15 Ea = 0 544 × 19 15/5
1
3386-3389
15 Ea = 0 544 × 19 15/5 714 × 10–4 = 18230
1
3387-3390
544 × 19 15/5 714 × 10–4 = 18230 8 J Since k = Ae-Ea/RT 0
1
3388-3391
15/5 714 × 10–4 = 18230 8 J Since k = Ae-Ea/RT 0 02 = Ae-18230
1
3389-3392
714 × 10–4 = 18230 8 J Since k = Ae-Ea/RT 0 02 = Ae-18230 8/8
1
3390-3393
8 J Since k = Ae-Ea/RT 0 02 = Ae-18230 8/8 314 × 500 A = 0
1
3391-3394
02 = Ae-18230 8/8 314 × 500 A = 0 02/0
1
3392-3395
8/8 314 × 500 A = 0 02/0 012 = 1
1
3393-3396
314 × 500 A = 0 02/0 012 = 1 61 The first order rate constant for the decomposition of ethyl iodide by the reaction C2H5I(g) ® C2H4 (g) + HI(g) at 600K is 1
1
3394-3397
02/0 012 = 1 61 The first order rate constant for the decomposition of ethyl iodide by the reaction C2H5I(g) ® C2H4 (g) + HI(g) at 600K is 1 60 × 10–5 s–1
1
3395-3398
012 = 1 61 The first order rate constant for the decomposition of ethyl iodide by the reaction C2H5I(g) ® C2H4 (g) + HI(g) at 600K is 1 60 × 10–5 s–1 Its energy of activation is 209 kJ/mol
1
3396-3399
61 The first order rate constant for the decomposition of ethyl iodide by the reaction C2H5I(g) ® C2H4 (g) + HI(g) at 600K is 1 60 × 10–5 s–1 Its energy of activation is 209 kJ/mol Calculate the rate constant of the reaction at 700K
1
3397-3400
60 × 10–5 s–1 Its energy of activation is 209 kJ/mol Calculate the rate constant of the reaction at 700K We know that log k2 – log k1 = a 1 2 1 1 2
1
3398-3401
Its energy of activation is 209 kJ/mol Calculate the rate constant of the reaction at 700K We know that log k2 – log k1 = a 1 2 1 1 2 303 E T T R        Subtracting equation (3
1
3399-3402
Calculate the rate constant of the reaction at 700K We know that log k2 – log k1 = a 1 2 1 1 2 303 E T T R        Subtracting equation (3 20) from (3
1
3400-3403
We know that log k2 – log k1 = a 1 2 1 1 2 303 E T T R        Subtracting equation (3 20) from (3 21), we obtain ln k2 – ln k1 = a 1 E RT – a 2 E RT ln k k E R T T 2 1 1 2 1 1 = −     a log
1
3401-3404
303 E T T R        Subtracting equation (3 20) from (3 21), we obtain ln k2 – ln k1 = a 1 E RT – a 2 E RT ln k k E R T T 2 1 1 2 1 1 = −     a log kk E R T T 2 1 1 2 2 303 1 1 = −     a (3
1
3402-3405
20) from (3 21), we obtain ln k2 – ln k1 = a 1 E RT – a 2 E RT ln k k E R T T 2 1 1 2 1 1 = −     a log kk E R T T 2 1 1 2 2 303 1 1 = −     a (3 22) log
1
3403-3406
21), we obtain ln k2 – ln k1 = a 1 E RT – a 2 E RT ln k k E R T T 2 1 1 2 1 1 = −     a log kk E R T T 2 1 1 2 2 303 1 1 = −     a (3 22) log kk E T T T T 2 1 2 1 1 2 =2 303 −     a R Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Example 3
1
3404-3407
kk E R T T 2 1 1 2 2 303 1 1 = −     a (3 22) log kk E T T T T 2 1 2 1 1 2 =2 303 −     a R Solution Solution Solution Solution Solution Solution Solution Solution Solution Solution Example 3 10 Example 3