Jawab soalan mengikut arahan yang diberikan dalam setiap bahagian. Questions should be answered according to the instructions given in each section.

Transcription

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 2014/2015 : SEMESTER 2 ACADEMIC SESSION 2014/2015 : SEMESTER 2 SCES1230 : KIMIA FIZIK I PHYSICAL CHEMISTRY I Juni 2015 June 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 12 soalan dalam 7 halaman yang dicetak) (This question paper consists of 12 questions on 7 printed pages)

2 BAHAGIAN A (50 MARKAH) SECTION A (50 MARKS) Jawab semua soalan. Answer all questions. 1. Di antara berikut, yang manakah fungsi laluan dan yang manakah bukan fungsi laluan? Which of the following entities are path functions, and which are not? (a) (c) (d) (e) Kerja Work Haba Heat Suhu Temperature Entalpi Enthalpy Isipadu Volume 2. Terangkan dengan ringkas Hukum-Hukum Termodinamik Sifar, Pertama, Kedua dan Ketiga. Explain briefly the Zeroth, First, Second, and Third Laws of Thermodynamics. 3. Lakarkan gambarajah-gambarajah P-V untuk proses-proses berikut: Sketch the P-V diagrams for the following processes: (12 markah/marks) (a) Adiabatik Adiabatic Isotermal Isothermal 2/7

3 (c) (d) Isokorik Isochoric Isobarik Isobaric (4 markah/marks) 4. Satu system yang terdiri daripada 1 mol gas monoatomik terkandung dalam satu omboh. Apakah perubahan suhu bagi gas tersebut jika haba, q = 50 J dan kerja, = 100 J? (R = JK 1 mol 1 ) A system which consists of 1 mole of a monoatomic gas is contained in a piston. What is the temperature change of the gas if heat, q = 50 J and work, w = 100 J? (R = JK 1 mol 1 ) (3 markah/marks) 5. Kirakan perubahan tenaga dalaman, U, untuk pembentukan NOCl(g) pada suhu 25 (R = JK 1 mol 1 ): Calculate the change in internal energy, U, for the formation of NOCl(g) at 25 (R = JK 1 mol 1 ): 1 2 N 2(g) O 2(g) Cl 2(g) NOCl(g) H = kj 6. Dalam penyediaan minuman teh, 600 g air pada suhu 90 telah dituangkan ke dalam 200 g teko china yang mempunyai suhu 20. Apakah suhu akhir air tersebut? (Nota: muatan haba tentu untuk teko china, c teko, ialah 840 Jkg 1 1, dan muatan haba tentu untuk air, c air, ialah 4185 Jkg 1 1. In preparing tea, 600 g of water at 90 is poured into a 200 g china pot at 20. What is the final temperature of the water? (Note: the specific heat capacity for the china pot, c pot, is 840 Jkg 1 1, and the specific heat capacity for water, c water, is 4185 Jkg /7

4 7. Kirakan t H 298 untuk tindakbalas 2FeO (p) + 1 O 2 Fe 2 O 3 (hematit), dengan diberi: Fe (p) + 1 O 2 FeO (p) t H 298 = kj 2Fe (p) + 3 O 2 Fe 2 O 3 (hematit) t H 298 = kj Calculate r H 298 for the reaction 2FeO (s) + 1 O 2 Fe 2 O 3 (hematite), given that: Fe (s) + 1 O 2 FeO (s) r H 298 = kj 2Fe (s) + 3 O 2 Fe 2 O 3 (hematite) r H 298 = kj (6 markah/marks) 8. Diberi bahawa S(sistem, gas unggul) = C v dt + R ln V 2, kirakan S (sistem) T 1 T V 1 untuk pengembangan isotermal berbalik untuk 1.00 mol gas unggul dari m 3 ke 0.100m 3 pada suhu 298 K. (R = JK 1 mol 1 ) T 2 C v Given that S(system, ideal gas) = dt + R ln V 2, calculate the S (system) for the T 1 T V 1 reversible isothermal expansion of 1.00 mole of an ideal gas from m 3 to m 3 at 298 K. (R = JK 1 mol 1 ) T 2 9. Apakah kriteria kespontanan bagi perubahan hala ke hadapan untuk perubahan tenaga Helmholtz, A, dan Gibbs, G? What are the criteria for the spontaneity of change in the forward direction in terms of the change in the Helmholtz, A, and Gibbs, G, energies? 4/7

5 BAHAGIAN B (50 MARKAH) SECTION B (50 MARKS) Jawab 2 soalan sahaja. Answer 2 questions only 10. (a) Suatu tindakbalas kimia diantara hydroxyetanolamin dan asid hidroklorik mempunyai mekanism berikut: A chemical reaction between hydroxyetanolamine and hydrochloric acid has the following mechanism: H 2 N-C 2 H 4 OH + HCl Cl-C 2 H 4 OH + NH 3 NH 2 CH 2 CH 2 OH + H + k 1 NH 3 + CH 2 CH 2 OH NH 3 + CH 2 CH 2 OH k 1 NH 2 CH 2 CH 2 OH + H + NH 3 + CH 2 CH 2 OH + Cl k 2 ClCH 2 CH 2 OH +NH 3 (iii) Terangkan apakah kadar penghampiran mantap (KPM). Explain what is steady state approximation (SSA). Dengan menggunakan KPM, berikan sebutan untuk bahan perantaraan di dalam mekanisma tindakbalas tersebut. Use the SSA to find an expression for the intermediate in the reaction mechanism. Di dalam kala masa manakah KPM tidak boleh digunakan? At which time interval does the SSA becomes invalid? (15 markah/marks) Persamaan Arrhenius adalah, k = Aexp[-E a /RT] The Arrhenius equation has the following expression, k = Aexp[-E a /RT] Terangkan apakah tenaga pengaktifan, E a / kj mol -1. Explain what is activation energy, E a / kj mol -1. Terangkan bagaimana suatu mangkin dapat mempercepatkan kadar tindakbalas dengan merujuk kepada persamaan Arrhenius. Explain how a catalysis accelerate the rate of reaction, by referring to the Arrhenius equation. (10 markah/marks) 5/7

6 11. (a) Suatu bateri magnesium-udara mempunyai notasi sel seperti berikut: A magnesium-air battery has a cell notation below: Mg (p) Mg(OH) 2 (ak) KOH (ak) O Pt (p) Mg (s) Mg(OH) 2 (aq) KOH (aq) O Pt (s) SCES1230 Tuliskan tindakbalas anodik dan katodik. Write the anodic and cathodic reactions. Dari tindakbalas separuh berikut: From these half-cell reactions: Anod: Pb (p) Pb 2+ (ak) + 2e - Anode: Pb (s) Pb 2+ (aq) + 2e - Cathod: 2H + (ak) + H 2 O 2 (c) + 2e - 2H 2 O (c) Cathode: 2H + (aq) + H 2 O 2 (l) + 2e - 2H 2 O (l) Berikan notasi sel. Give the cell notation. (10 markah/marks) Terangkan yang berikut: Explain the following: (iii) Keupayaan simpangan cecair. Liquid junction potential. Litar-pintas di dalam bateri. Short-circuiting in battery. Kepentingan membrane pemisah di dalam rekabentuk batteri. The importance of a membrane separator in battery design. (15 markah/marks) 12. (a) Suatu aluminum-udara batteri mempunayi sel notasi seperti berikut: An aluminum-air battery has the following cell notation: Al (p) 4Al(OH) 4 - (ak) KOH (ak) O Pt (p) Al (s) 4Al(OH) 4 - (aq) KOH (aq) O Pt (s) Anod: Al (p) + 4OH - (ak) Al(OH) 4 - (p) + 3e - Anode: Al (s) + 4OH - (aq) Al(OH) 4 - (s) + 3e - 6/7

7 Katod: O + 2H 2 O (c) + 4e - 4OH - (ak) Cathode: O + 2H 2 O (l) + 4e - 4OH - (aq) (iii) Tuliskan persamaan Nernst untuk bateri aluminium-udara. Write the Nernst equation for the aluminium-air battery. Sekiranya kepekatan KOH adalah 8 mol dm -3, kirakan aktiviti larutan dengan menggunakan persamaan penghad Debye Huckel, log 10 γ ± = -A Z +.Z - I 1/2. If the KOH concentration is 8 mol dm -3, calculate the activity for the solution using the Debye Huckel limiting law, log 10 γ ± = -A Z +.Z - I 1/2. Kirakan keupayaan sel keseimbangan sekiranya tekanan oksijen adalah 1 atm. Gunakan aktiviti dan bukan kepekatan di dalam pengiraan. Calculate the equilibrium cell potential if the oxygen pressure is 1 atm. Use activities and not concentrations in the calculation. O 2 (p) + 2H 2 O (c) + 4e - 4OH - (ak) O 2 (s) + 2H 2 O (l) + 4e - 4OH - (aq) Al(OH) - 4 (p) + 3e - 4Al (p) + 4OH - (ak) Al(OH) - 4 (s) + 3e - 4Al (s) + 4OH - (aq) E θ / V = 0.40 vs. SHE E θ / V = 0.40 vs. SHE E θ / V = vs. SHE E θ / V = vs. SHE R = J mol -1 K -1, T = 298 K, F = 96,500 C mol -1, 1 atm = N m -2, A = (mol kg -1 ) -1/2 R = J mol -1 K -1, T = 298 K, F = 96,500 C mol -1, 1 atm = N m -2, A = (mol kg -1 ) -1/2 (15 markah/marks) Berikan dua kesan yang merendahkan konduktiviti ion (k / S m -1 ) apabila kepekatan elektrolit menjadi besar. Give two effects which lower the ionic conductivity (k / S m -1 ) when the electrolyte concentration becomes very large. Untuk larutan berkepekatan tinggi, terangkan kenapa aktiviti, dan bukan kepekatan yang mesti digunakan di dalam pengiraan. In very large concentrations, explain why activity, instead of concentration must be used. (10 markah/marks) TAMAT END 7/7