SCES1230 : KIMIA FIZIK I PHYSICAL CHEMISTRY I

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1 UNIVERSITI MALAYA UNIVERSITY OF MALAYA PEPERIKSAAN IJAZAH SARJANA MUDA SAINS EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE PEPERIKSAAN IJAZAH SARJANA MUDA SAINS DENGAN PENDIDIKAN EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE WITH EDUCATION SESI AKADEMIK 2012/2013 : SEMESTER 2 ACADEMIC SESSION 2012/2013 : SEMESTER 2 : KIMIA FIZIK I PHYSICAL CHEMISTRY I Jun 2013 June 2013 MASA : 2 jam TIME : 2 hours ARAHAN KEPADA CALON : INSTRUCTIONS TO CANDIDATES : Kertas soalan ini mengandungi Bahagian A dan B. This paper consists of Section A and B. Jawab soalan mengikut arahan yang diberikan dalam setiap bahagian. Questions should be answered according to the instructions given in each section. (Kertas soalan ini mengandungi 4 soalan dalam 5 halaman yang dicetak) (This question paper consists of 4 questions on 5 printed pages)

2 BAHAGIAN A (50 MARKAH) SECTION A (50 MARKS) Jawab semua soalan. Answer all questions. 1. (a) Takrifkan sifat intensif dan sifat ekstensif. Berikan contoh yang sesuai dalam penjelasan anda. Define intensive property and extensive property. Give suitable examples in your explanation. (4 markah/marks) Nyatakan Hukum Kedua Termodinamik. Tunjukkan bagi sesuatu proses boleh berbalik, State the Second Law of Thermodynamic. Show that for a reversible process U = T S-p V H = T S V p Kirakan perubahan entropi apabila 2.00 mol Al dipanaskan dari 30 C hingga 50 C pada tekanan tetap, diberikan C p bagi Al 20.6 J K -1 mol -1. Calculate the entropy change when 2.00 mol of Al is heated from 30 C to 50 C at constant pressure, given that C p of Al is 20.6 J K -1 mol -1. (12 markah/marks) (c) Kirakan H f, entalpi pembentukan Al 2 O 3 daripada persamaan termokimia berikut. Calculate H f, the enthalpy of formation for Al 2 O 3 from the following thermochemical equation. Al(s) + ¾ O 2 (g) ½ Al 2 O 3 (s) H = kj Jika H f bagi CuO(s) adalah kj mol -1, kirakan haba tindak balas bagi perubahan kimia berikut. If the H f of CuO(s) is kj mol -1, calculate the heat of reaction for the following chemical change: 2Al(s) + 3CuO(s) Al 2 O 3 (s) + 3Cu(s) (9 markah/marks) 2/5

3 2. (a) Bagi tindak balas fasa gas berikut yang berlaku pada suhu tetap: The following reaction in gas phase occurs at fixed temperture: 3 H 2 (g) + N 2 (g) 2 NH 3 (g) H = kj. Kirakan U bagi perubahan kimia itu. Calculate U for the chemical change. (6 markah/marks) Takrifkan istilah G, tenaga bebas Gibb. Bagaimanakah G boleh menunjukkan sama ada sesuatu proses boleh berlaku secara spontan? Bagi perubahan keadaan berikut: Br 2 (l) Br 2 (g), ΔH = kj/mol, ΔS = 93.2 J/mol.K Define the term G, Gibb s free energy. How can G be used to show whether a process can occur spontaneously? For the following change in state: Br 2 (l) Br 2 (g), ΔH = kj/mol, ΔS = 93.2 J/mol.K Bolehkah Br 2 (l) mendidih secara spontan pada 35 C? Can Br 2 (l) boil spontaneously at 35 C? Berapakah takat didih bromin? What is the boiling point of bromine? (9 markah/marks) (c) 16 g gas oksigen dibenarkan mengembang secara isotermal dan berbalik pada 27 C dan tekanan gas telah turun daripada100 kpa ke 10 kpa. 16 g of oxygen gas is allowed to expand isothermally and reversibly at 27 C and the gas pressure has dropped from 100 kpa down to 10 kpa. Kirakan Calculate w, U (iii) q (iv) H (v) S, dan/and (vi) G (10 markah/marks) 3/5

4 BAHAGIAN B (50 MARKAH) SECTION B (50 MARKS) Jawab semua soalan. Answer all questions. 3. (a) Bincang hubungan antara persamaan Arrhenius dan teori perlanggaran. Discuss the relation between Arrhenius equation and the collision theory. (5 markah/marks) Data bagi tindak balas A + B + C hasil pada 70 o C diberi di bawah: Data of reaction A + B + C products at 70 o C are given below: Kadar awal / M s -1 Initial rate [A] [B] [C] 6.76 x x x x Tentukan Determine (iii) hukum kadar and pemalar kadar. the rate law and rate constant. tenaga pengaktifan. the activation energy. ulas kesan suhu terhadap pemalar kadar. comment on the effect of temperature on the rate constant. [Diberi pada 90 o C, pemalar kadar ialah 1.58 x 10-4 M -2 s -1 ] [Given at 90 o C, the rate constant is 1.58 x 10-4 M -2 s -1 ]. (12 markah/marks) (c) Apakah yang dimaksudkan dengan tindak balas asas dan mekanisma tindak balas? What is meant by elementary reaction and reaction mechanism? 4/5

5 Penguraian hidrogen peroksida dimangkinkan dengan ion iodide: The decomposition of hydrogen peroxide is catalyzed by iodide ion: 2 H (aq) 2H 2 O (l) + O 2 (g) Rate = k [H 2 O 2 ] [I] Cari mekanisme yang mungkin dan kenalkan perantaraannya. Find a possible mechanism and identify the intermediate. (8 markah/marks) 4. (a) Bincang hubungan antara kekonduksian molar and kepekatan untuk kedua-dua elektrolit kuat dan lemah. Discuss the relationship between molar conductivity and electrolyte concentration for both strong and weak electrolytes. (10 markah/marks) Tindak balas redoks berikut berlaku dalam satu sel voltaic pada 25 o C: The following redox reaction occurs in a voltaic cell at 25 o C: Fe 3+ (aq) + Cd(s) Fe 2+ (aq) + Cd 2+ (aq) (iii) Lukis gambarajah berlabel untuk sel voltaic tersebut dan tulis notasi selnya. Draw a labeled diagram for the voltaic cell and write the cell notation. Kira keupayaan sel dan perubahan tenaga bebas piawai bagi tindak balas sel tersebut apabila [Fe 3+ ] = 6.2 x 10-5 M, [Fe 2+ ] = 0.35 M, [Cd 2+ ] = 0.75 M. Diberikan Fe 3+ Fe 2+, E o = 0.77 V dan Cd 2+ Cd, E o = 0.40 V. Calculate the cell potential and the standard free energy change of the cell reaction when [Fe 3+ ] = 6.2 x 10-5 M, [Fe 2+ ] = 0.35 M, [Cd 2+ ] = 0.75 M. Given Fe 3+ Fe 2+, E o = 0.77 V and Cd 2+ Cd, E o = 0.40 V. Apakah kesan terhadap keupayaan sel jika suhu sistem sel bertambah? What is the effect on the cell potential if temperature of the cell system is increased? (15 markah/marks) TAMAT END 5/5