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 2014/2015 : SEMESTER 1 ACADEMIC SESSION 2014/2015 : SEMESTER 1 SCES1230 : KIMIA FIZIK I PHYSICAL CHEMISTRY I Disember 2014/Januari 2015 December 2014/January 2015 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 5 soalan dalam 6 halaman yang dicetak) (This question paper consists of 5 questions on 6 printed pages)
Jawab semua soalan. Answer all questions. BAHAGIAN A (50 MARKAH : TERMODINAMIK SECTION A (50 MARKS) : THERMODYNAMICS 1. (a) Takrifkan sifat ekstensif dan sifat intensif. Berikan contoh yang sesuai dalam penjelasan anda. Define extensive property and intensive property. Give suitable examples to illustrate your explanation. (5 markah/ marks) Nyatakan Hukum Pertama Termodinamik. Tunjukkan bahawa U = q v State the First Law of Thermodynamic. Show that U = q v (5 markah/ marks) (c) Jadual berikut memberikan data haba pembentukan beberapa sebatian. Apakah maksudnya haba pembentukan? Gunakan data dalam jadual untuk mengira haba pembakaran fenol. The following table list the heats of formation of some compounds. What is meant by the heat of formation? Use the given data to calculate the heat of combustion of phenol. C 6 H 5 OH(c) +7 O 2 (g) 6CO 2 (g) + 3H 2 O (c) C 6 H 5 OH(l) +7 O 2 (g) 6CO 2 (g) + 3H 2 O (l) Sebatian/ Compound H f / kj/mol CO 2 (g) -393.5 H 2 O (c, l) -285.8 C 6 H 5 OH(l) -165.0 (7 markah/ marks) (d) Sebutkan Hukum Ketiga Termodinamik. Bagaimana Hukum ini boleh digunakan untuk menentukan entropi mutlak bagi sesuatu unsur atau sebatian pada sesuatu suhu? 0.2 mol gas nitrogen berkembang secara berbalik dari 4.5 L ke 9.0 L pada suhu tetap 25 C. Kirakan State the Third Law of Thermodynamics. How can it be applied to determine the absolute entropy of an element or a compound at a given temperature? 0.2 mol of nitrogen gas was expanded reversibly from 4.5 L to 9.0 L at constant temperature of 25 C. Calculate 2/6
kerja terlibat. the work involved, perubahan entropi. the change in entropy. (8 markah/ marks) 2. (a) Takrifkan istilah tenaga bebas Gibb. Bagaimana perubahan tenaga bebas Gibb boleh meramalkan arah tindak balas yang berlaku secara spontan? Define the term Gibb s free energy. How can the change in Gibb s free energy be used to predict the direction of a spontaneous reaction? (5 markah/ marks) Dalam suatu proses industri, metanol boleh disediakan melalui tindak balas karbon monoksida dan hidrogen di bawah suhu tertentu. In an industrial process, methanol can be prepared by reacting carbon monoxide with hydrogen under suitable temperture. CO(g) + 2H 2 (g) = CH 3 OH(g) H = -91.0 kj mol -1 Perubahan entropi tindak balas S = -219 J K -1 mol -1, Bolehkah tindak balas itu dijalankan pada The entropy change of the reaction S = -219 J K -1 mol -1, Can the reaction be carried out at 100 C? 150 C? (6 markah/ marks) (c) 2 g gas helium mengembang secara isotermal pada suhu tetap 40 C dari isipadu 2L ke 4L dalam suatu proses berbalik. Kirakan 2 g of helium gas has undergone isothermal expansion at 40 C from a volume of 2L to 4L in a reversible manner. Calculate U, w, (iii) q, (iv) H, (v) S, (vi) G dan (vii) A bagi perubahan yang telah berlaku. [Berat atom He = 4] U, w, (iii) q, (iv) H, (v) S, (vi) G and (vii) A for the change that has occurred. [Atomic weight He=4] (14 markah/ marks) 3/6
BAHAGIAN B (50 MARKAH) SECTION B (50 MARKS) Jawab 2 soalan sahaja. Answer 2 questions only 3. (a) Terangkan larutan manakah lebih bersifat tidak unggul dalam keadaan kekuatan ion yang sama: Na 3 PO 4 or KCl? Explain which solution has more non-ideal behavior at the same ionic strength: Na 3 PO 4 or KCl? (iii) Berikan penerangan tentang kefahaman yang betul mengenai kekonduksian molar pada kelarutan infinit, Λ o / S m 2 mol -1. Explain the correct understanding of the parameter, molar conductivity at infinite dilution, Λ o / S m 2 mol -1. Lakaran gambarajah suatu ion (+ or -) di dalam larutan yang pekat, di mana γ ± adalah kurang dari nilai satu. Sketch a diagram of an ion (+ or -) in very concentrated electrolyte solution, where the γ ± is less than one. (15 markah/ marks) Dari notasi sel, berikan tindak balas anod dan katod From the cell notation give the anodic and cathodic reactions Zn (p) ZnO (p) OH - (ak) O 2 (ak) Pt (p) Zn (s) ZnO (s) OH - (aq) O 2 (aq) Pt (s) Sn (p) Sn 2+ (ak) OH - (ak) Mn 2 O 3 (p) MnO 2 (p) Sn (s) Sn 2+ (aq) OH - (aq) Mn 2 O 3 (s) MnO 2 (s) (10 markah/ marks) 4. (a) Terangkan yang berikut: Explain the following: tindak balas pseudo tertib pertama. pseudo first order reaction. 4/6
langkah penentu kadar. rate determining step. persamaan Arrhenius, k = A exp[-e A /RT]. Arrhenius equation, k = A exp[-e A /RT]. (15 markah/ marks) Dari tindak balas berkiut, tuliskan tindak balas katod dan anod From the chemical equations below, write the cathodic and anodic reactions 2Al (p) + 2MnO 4 - (ak) + H 2 O (ak) Al 2 O 3 (p) + 2MnO 2 (p) + 2OH - (ak) 2Al (s) + 2MnO 4 - (aq) + H 2 O (aq) Al 2 O 3 (s) + 2MnO 2 (s) + 2OH - (aq) H 2 O 2 (aq) + HCOOH (aq) CO 2 (g) + 2H 2 O (aq) H 2 O 2 (ak) + HCOOH (ak) CO 2 (g) + 2H 2 O (ak) (10 markah/ marks) 5. (a) Suatu sel kepekatan ion vanadium mempunyai notasi sel yang berikut: A vanadium ion concentration cell has this cell notation V (p) V 2+ (ak), Cl - (ak) V 2+ (ak), Cl - (ak) V (p) V (s) V 2+ (aq), Cl - (aq) V 2+ (aq), Cl - (aq) V (s) Di mana symbol adalah membrane separa telap, kepekatan VCl 2 di anod dan katod adalah 0.005 M and 1 M masing-masing. Keupayaan simpangan cecair adalah lebih kurang 0.005 V. Where the symbol is a semi permeable membrane, the VCl 2 concentration in the anode and cathode are 0.005 M and 1 M respectively. The estimated liquid junction potential of the cell is 0.005 V. Kirakan aktiviti ion untuk V 2+ pada anod dan katod. Calculate the activities of V 2+ at the anode and cathode. Kirakan beza upaya di antara anod dan katod. Calculate the potential difference between the anode and cathode. 5/6
(iii) Apakah kepekatan anod dan katod apabila keupayaan sel menjadi sifar. What are the anode and cathode concentrations when the cell potential reaches zero. (15 markah/ marks) Terangkan apakah yang dimaksudkan dengan keupayaan simpangan cecair. Explain what is liquid junction potential. Kirakan keupayaan piawai untuk tindak balas berikut. Calculate the standard equilibrium potential of this reaction. V 3+ (ak) + 3e - V (p) V 3+ (aq) + 3e - V (s) Hukum Penghad Debye-Huckel, log 10 (γ ± ) = -(0.509) Z +.Z - I 1/2 Debye-Huckel limiting law, log 10 (γ ± ) = -(0.509) Z +.Z - I 1/2 I 1 z 2 m i i 2 i V 2+ (aq) + 2e - V (s) E ϴ / V = -1.2 vs SHE V 3+ (aq) + e - V 2+ (aq) E ϴ / V = -0.225 vs SHE R = 8.3142 J mol -1 K -1, T = 298 K. (10 markah/ marks) TAMAT END 6/6