Your Teacher!! : Agus Setiabudi Tempat Tgl. Lahir : Tasikmalaya, 03 Agustus 1968

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1 Your Teacher!! Nama : Agus Setiabudi Tempat Tgl. Lahir : Tasikmalaya, 3 Agustus 1968 Pendidikan : S1 Kimia IKIP Bandung ( ) S2 Kimia ITB, Kimia Fisika, ( ) S3 Delft University of Technology Nederland, Katalisis ( ) CV 1

2 Apa yang dipelajar dalam Kuliah Kimia Fisika? Apa yang dipelajari dalam Kuliah Termodinamika? Apa yang akan dipelajari dalam Kuliah Kinetika? 2

3 Energi yangt menyertai perubahan materi Membahas mengapa reaksi dapat terjadi atau tidak terjadi, jadi hanya melihat keadaan awal dan keadaan akhir tanpa memperhatikan proses 3

4 Perubahan fisik spt perubahan fasa, sifat koligatif Keadaan fisik suatu reaksi spt. Suhu, tekanan Aspek fisika dalam sistem kimia dengan menggunakan matematika sbg alat bantu T,P, V, Energi, Kecepatan reaksi, Kesetimbangan 4

5 Kimia Fisika - Cabang ilmu kimia yang menggunakan prinsip dan hukum fisika untuk mempelajari perilaku system kimia - Menggunakan Matematika sebagai Alat - It includes the qualitative and quantitative study, both experimental and theoretical, of the general principles determining the behavior of matter, particularly the transformation of one substance into another. 5

6 Senyawa Kimia Chemical Kinetics and Thermodynamics f G 298 C 2 H 5 OH C 6 H 12 O CO H 2 O -228,57 1. Parameter apa yang menentukan kespontanan reaksi? 2. Apakah reaksi antara C2H5OH and O2 merupakan reaksi yang spontan? Those question shows you the importance of Kinetics (Activation Energy) 6

7 Physical Chemistry Topics Gas Laws Basic Thermodynamics Chemical Equilibrium Phase Equilibrium Mult. Phase Equilibrium Electro Chem Thermodynamics Statistical Mechanics Basic Quantum Chemistry Atomic Structure and Chemical Bonding Quantum Chemistry Radiochemistry Kinetics Reaction Rate and Mechanism (Time as variable) Introduction to Catalysis 7

8 Kinetics vs Thermodynamics Thermodynamics show why a reaction wants to proceed. Kinetics can explain how it proceeds. The two topics are complementary: you will need both to understand chemistry. 8

9 Thermodynamics vs Kinetics 1 f G298 H2 O( g) 228,572 kj mol Means that G for the formation of H 2 O < : H2( g) O2 ( g) H2O( g) Spontaneous???? 9

10 Refferensi dan Pelaksanaan Perkuliahan 1. Gilbert Castelan, Physical Chemistry, 2. Ira Levine, Physical Chemistry 3. Sumber-sumber Lain Urutan dan pendekatan sangat mungkin tidak sesuai dengan buku!!!! 1

11 Chemical Kinetics A study on reaction rate and mechanism Introduction Pengukuran Laju Reaksi Penentuan Hukum Laju Pengaruh Temperatur Mekanisme Reaksi Catalysis 11

12 Kinetics - the rates of chemical reactions How fast does a reaction go? Does the rate change over time? Can it be influenced? What does all this say about how the reaction proceeds? 12

13 Introduction What is reaction rate? How to determine? Example: Your Laboratory Experiment H 2 O 2 (aq) H 2 O(l) + 1/2O 2 (g) 13

14 Pengukuran dan Penentuan Laju Reaksi Our Laboratory Practice: H 2 O 2 H 2 O + O 2 O 2 gas bubble H 2 O 2 14

15 Pengukuran dan Penentuan Laju Reaksi Our Laboratory Practice: H 2 O 2 H 2 O + O 2 O 2 gas H 2 O 2 15

16 Pengukuran dan Penentuan Laju Reaksi Our Laboratory Practice: H 2 O 2 H 2 O + O 2 O 2 gas H 2 O 2 16

17 V O 2 (ml) Pengukuran dan Penentuan Laju Reaksi Our Laboratory Practice: H 2 O 2 H 2 O + O 2 O 2 gas H 2 O Time (min) 17

18 H 2 O 2 Mass (g) Pengukuran dan Penentuan Laju Reaksi Our Laboratory Practice: H 2 O 2 H 2 O + O 2 13,356 g Time (min) 18

19 Reaction Rate: Definition Reactant Product Rate of reactant consumption -d[r]/dt Rate of product formatiom: d[p]/dt 19

20 Reaction Rate: Definition For the reaction: A + 2B 3C + D B is consumed twice faster than A; C is produce three times faster than D. To have a numeric value appropriate for overall reaction, a new variable r is defined: r = d[d]/dt = 1/3 d[c]/dt r = d[a]/dt = ½ d[b]/dt 2

21 Exercise 21

22 Exercise Jika hasil percobaan, pada keadaan STP, untuk reaksi H 2 O 2 H 2 O + ½ O 2 Adalah sbb Volume O 2 /ml (stp): Waktu (menit) : ~ Tentukan: a. Laju reaksi rata-rata penguraian H 2 O 2 b. Laju reaksi rata-rata antara 1 dan 25 menit c. Laju reaksi awal! d. Laju sesaat pada t = 15 menit 22

23 Tugas!!!! Jelaskan langkah yang bisa ditempuh untuk mengukur laju reaksi: CH 3 COCH 3 + I 2 CH 3 COCH 2 I + HI 23

24 Example of Measurement Equipment Applicable Reaction : C + O 2 CO/CO 2 CO + ½ O 2 CO 2 NO + ½ O 2 NO 2 O 2 Heater IR NO Pt Catalyst Heater Ir Thermocouple 24

25 Reaction Rate: Definition and Order The decomposition of nitrosyl bromide (NOBr) can be followed manometrically. An example of this experimental results is shown a follows: t (s) [NOBr](mol/L): a. Use graphical methods to estimate the rate at 3 s and 7 s! b. Determine the reaction order 25

26 Rate law Rate Law (Rate Equation); a mathematical expresion that relates reaction rate as a function of reactant concentration r = k[a] m [B] n Reaction rate is normally proportional with concentration and has simple power number This power number is called reaction order For the rate law = k[a] m [B] n, the reaction has m order with respect to A, n order with respect to B the overal reaction has m+n order 26

27 Rate Law; Integration form Describe reactant concentration (ex. [A]) as a function of time (t); The differential definition for the rate is equated to the rate law, For zero order reaction: r da [ ] dt k[ A] 27

28 Rate Law; Integration form r da [ ] dt k[ A] [ A] da t kdt [ A] [A] - [A] = -kt [A] = [A] - kt. Plotting [A] vs. t gives a straight line with slope = -k. 28

29 First Order Reaction; Integration da [ ] ka [ ] dt [ A] [ A] da [ ] [ A] t kdt n = 1 (first order) A produk ln[ A] t ln[ A] kt [ A] t ln [ A ] kt [A] = [A] e -kt 29

30 First Order Reaction; Integration ln[ A] t ln[ A] kt ln[ A] t kt ln[ A] y = mx + c n = 1 (first order) A produk Integrated form of the 1st order rate expression [A] = [A] e -kt 3

31 ln([a]/[a] ) A Straight-Line Plot for a First- Order Reaction For first order reaction, ln([a]/[a] ) = -kt Plott ln [A] vs t result in a straight line So does ln ([A]/[A] ) vs. t So does plotting the log of pressure of a reactant t/s 4 Such a plot can be used to determine k and to evaluate the order 31

32 Bentuk Kurva reaksi orde 1 ln[ A] t kt ln[ A] [ A] t ln [ A ] kt Intercept = ln[a] t / s ln[ A] t -slope = -k [ A] t ln [ A ] -slope = -k? t / s Other useful forms 32

33 Exercise E7.5 The concentration of N 2 O 5 in liquid bromine varied with time as follows: t/s [N 2 O 5 ]/M Show that the reaction is first order in respect to N 2 O 5 and determine the rate constant. 33

34 What can we conclude about RATE LAWS versus INTEGRATED RATE EXPRESSSIONS?? a rate law can tell us the rate of a reaction, once the composition of the reaction mixture is known An integrated rate expression can give us the concentration of a species as a function of time. It can also give us the rate constant and order of the reaction by plotting the appropriate graph 34

35 Kinetika Orde dua; bentuk integrasi Kinetika Orde 2 2A produk Hukum laju: d[a]/dt = -k[a] 2 A A da [ ] 2 [ A] t 1 1 [ A] [ A] kdt kt 1 [ A] t 1 [ A] 1 1 [ A] [ A ] kt t 35

36 Kinetika Orde dua; bentuk integrasi Kinetika Orde 2 2A produk 1 1 [ A] [ A ] kt [ A] [ A] 1 [ A] kt [ A] 1 [ A] 1 [ A] kt 36

37 2 nd Order Rate Laws 5.2 The most prominent difference between 1 st and 2 nd orders is the rate at low concentration of A, much slower for 2 nd order 2 nd order decay processes die out long before they would have if they were 1 st order decays, especially important to the atmosphere, as many pollutants disappear by 2 nd order laws 37

38 Exercise Data reaksi dimerisasi 2A A 2 suatu senyawa nitril oksida, ditunjukan pada tabel berikut: [A]/(mmol/L) 68, 5,2 4,3 33,1 28,4 22,3 18,7 14,5 t/min Tentukan orde reaksinya, dengan metode yang telah di pelajari! 38

39 Penentuan Hukum Laju Cara Waktu paruh Berlaku untuk persamaan laju r = k[a] n Orde [A] = [A] - kt. Substitusi t dengan t ½ dan [A] dengan ½[A] ½[A] = [A] kt 1/2 [ A ] t 1 2 2k 39

40 Penentuan Hukum Laju Cara Waktu paruh Orde 1 A ln = -kt A Substitusi t dengan t ½ dan [A] dengan ½[A] A ln = -kt1/2 2A t 12 ln 2 k 4

41 Hence, t 1/ 2 ln 2 k or t 1/ k What is/are the main point(s) to note from this expression?? For a 1 st order reaction, the half-life is independent of reactant concentration but dependent on k. The half-life is constant for a 1 st order reaction concentration [A] [A] /2 t 1/2 Recall: [A] t = [A] e -kt [A] /4 [A] /8 t 1/2 t1/2 time 41

42 Penentuan Hukum Laju Cara Waktu paruh Orde A A kt Substitusi t dengan t ½ dan [A] dengan ½[A] A 1 1 A A kt 1/ 2 kt 1/ 2 t 12 = 1 k[a] 42

43 Penentuan Hukum Laju Cara Waktu paruh Untuk reaksi orde n: da k [ A] n dt n [ A] [ A] n 1 1 n 1 kt [ A] [ A] n [ A] d[ A] x (1 n)[ A] n 1 t k dt n [ A] [ A] n 1 n 1 1 [ A] ( n 1) kt ut. n 1 Untuk [A] = ½ [A] dan t = t 1/2 n t1/ 2 n 1 ( n 1)[ A] k ut. n 1 43

44 Kinetika Orde dua; bentuk integrasi Bentuk lain dari reaksi orde 2 adalah r = k[a][b]. More difficult to integrate!!! Untuk Reaksi: aa + bb produk r 1 da [ ] a dt k[ A][ B] Persamaan ini memiliki 3 variable: [A], [B], dan t Supaya persamaan dapat diintegrasi [B] harus dieliminasi dengan menghubungkannya dg [A] 44

45 Kinetika Orde dua; bentuk integrasi perbandingan[ A] dan[ B] yang bereaksi : [ A] [ B] a b atau b a ([ B ] [ B]) ([ A ] [ A]) atau r 1 da [ ] a dt k[ A][ B] [ ] [ ] b b B B [ A] [ A ] a a Integrasi persamaan hk laju : 1 d[ A] b b k[ A] [ B] [ A] [ A] a dt a a 45

46 Kinetika Orde dua; bentuk integrasi Integrasi persamaan hk laju : [ A] 1 1 a b b [ A] [ B ] [ A ] [ A] a a d[ A] [ A] Integrasi persamaan hk laju menghasilkan : t kdt [ B] 1 [ B] ln ab [ ] b [ A ] [ A ] [ A] kt 46

47 Exercise The initial rate of a reaction depended on the concentration of a substance J as follows. [J] /(1-3 M) r /(1-7 M s -1 ) Find the order of the reaction with respect to J and the rate constant. r = k[j] n, so log r = n log [J] + log k log [J] log r log r goes up twice as fast as log [J], so n = 2 and log k =.56-2(.7) = -.84; k =.15 M -1 s -1 47

48 Experimental Determination of Rate Law Isolation Method: All reactant is made excessive, except a reactant under investigation For the reaction: ma + nb product If A and B are dilutes solution: r = k[a] x [B] y If the reaction is proceed in excess of B: r = k[a] x This reaction order obtained is called pseudo- order The various pseudo- orders can be put together to give the overall order. 48

49 Determination of Rate Law Initial Rate Methods: The rate is measured at the beginning of reaction with some variations in reactant initial concentrations: Exercise: For the reaction 2A + B + C product, the initial reaction as a function of initial concentration is shown as follow (c o =1mol/dm 3 ): Expt. nr [A] o /c o,2,6,2,6 [B] o / c o,3,3,9,3 [C] o / c o,15,15,15,45 1 r o / (c o /s),6 1,81 5,38 1,81 49

50 Contoh soal (1) Dekomposisi fasa gas asetaldehid telah dipelajari pada temperatur 791 K. Hasil pengukuran dari dua percobaan adalah: Konsentrasi awal/(mol/l) 9,72 x 1-3 4,56x1-3 Waktu paruh/detik Tentukan orde reaksi dan konstanta laju reaksinya! 5

51 Contoh soal (1) Untuk reaksi A + B C + D, experimen dengan: [A ] = 4 mmol/l, dan [B ] =,4 mmol/dm menghasilkan data t/s ~ [C]/mmol.L [A]/mmol.L [B] /mmol.l Pada [A ] =,4 mmol/l, dan [B ] = 4 mmol/dm menghasilkan data t/s ~ [C]x1/mmol.L -1 2, 3, 3,5 4, Tentukan hukum laju dan konstanta laju 51

52 Exercise E7.6 The half-life of a substrate in a certain enzymecatalyzed first order reaction is 138 s. How long is required for the initial concentration of substrate, which was 1.28 mmol/l, to fall to.4 mmol/l? 52

53 Untuk reaksi: 2A + B C + D + 2E, data untuk reaksi yang berlangsung pada [A] = 8 mmol dm -3, dan [B] = 2 mmol dm -3 adalah: t/1s [B]/[B],836,745,68,582,452,318 Sedangkan data untuk reaksi yang berlangsung pada [B] = 6 mmol dm -3, dan [A] = 2 mmol dm -3 adalah: t/1s [A]/[A].91,787,593,453 Tentukan orde reaksi dan konstanta laju reaksi tersebut! 53

54 Your Teacher 54