Chm 270

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AS/SEP 2011/CHM270

#t|
UNIVERSITI TEKNOLOGI MARA FINAL EXAMINATION

COURSE COURSE CODE EXAMINATION TIME

PHYSICAL CHEMISTRY CHM270 SEPTEMBER 2011 2 HOURS

INSTRUCTIONS TO CANDIDATES 1. This question paper consists of two (2) parts: PART A (10 Questions) PART B (5 Questions) 2. Answer ALL questions from all two (2) parts: i) Answer PART A in the Objective Answer Sheet. ii) Answer PART B in the Answer Booklet. Start each answer on a new page. Do not bring any materials into the examination room unless permission is given by the invigilator. Please check to make sure that this examination pack consists of: ) ) ) iv) the Question Paper a one - page Appendix an Answer Booklet - provided by the Faculty an Objective Answer Sheet - provided by the Faculty

3.

4.

DO NOT TURN THIS PAGE UNTIL YOU ARE TOLD TO DO SO
This examination paper consists of 7 printed pages
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AS/SEP 2011/CHM270

PART A Identify the conjugate base of HP042" in the following reaction. HC03" A. B. C. D. H20 HCCV H 2 C0 3 PO43+ HPO42" = 5 ^ H2CO3 + P0 4 3 '

1.

2.

A 0.10 M HF solution is 8.4% ionized. Calculate the H+ ion concentration. A. B. C. D. 8.4x10" 3 M 8.4x10" 2 /W 0.84 M 0.10 M

3.

Calculate the pH of a buffer solution which contains 0.25 M benzoic acid, C6H5C02H and 0.15 M sodium benzoate, C6H5C02Na. Given Ka = 6.5 x 10"5. A. B. C. D. 4.83 4.19 3.97 3.40

4.

Which one of the following species has the highest entropy, S° at 25°C? A. B. C. D. CH3OH(l) CO(g) MgC03(s) H20(l)

5.

Which of the following equations represent a reaction that gives the heat of formation of H2S04(l)? A. B. C. D. 2H(g) + S(g) + 40(g) - * H2S04(l) H2(g) + S(g) + 202(g) -> H2S04(l) H2S04(l) -> 2H(g) + S(s) + 40(g) H2(g) + S(s) + 202(g) ^ H2S04(l)

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AS/SEP 2011/CHM270

6.

The following factors affect the rate of a chemical reaction except A. B. C. D. the concentration of the reactant. the temperature of the experiment. the volume of the reactions. the size of the particles of solid used as the reactant.

7.

A first reaction has a rate constant of 7.5 x 10"3 s"1. The half-life of this reaction is A. B. C. D. 3.8x1fJ- 1 s 92.4 s 120 s 6.9x10" 3 s

8.

Which of the following mixtures of liquid is expected to obey Raoult's Law? A. B. C. D. Ethanol and water Ethanol and propanone Benzene and ethylbenzene Hydrochloric acid and water

9.

What is the value of the degree of freedom, F at the triple point in the phase diagram of H 2 0? A. B. C. D. 0 1 2 3

10.

What is the name of the colloid if the dispersed phase is a solid and the dispersion medium is a liquid? A. B. C. D. Sol Aerosol Emulsion Foam

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PARTB

QUESTION 1 a) i) Define an acid according to Lewis theory. (1 mark) ii) Write the ionization equation of ammonia in water and calculate the pH value of a 0.10 M ammonia solution. (Kb NH3 = 1.8 x 10"5) (2 marks) Calculate the pH of a 0.200 M solution of NH4CI. The Kb value of ammonia is 1.8x10- 5 andK w =1.0x10" 1 4 . (3 marks)

i)

b)

Consider the following reaction: H2(g) i) +
1

/202(g)

-> H20(l)

AH = -287 kJ mol"1

Is the reaction exothermic or endothermic? (1 mark)

ii)

What is the value of AH for the reaction : 2H20(I) -> 2H2(g)

+

02(g) (1 mark)

c)

Calculate AH for the reaction below: C2H4(g) + H2(g) -> C2H6(g)

Given the following reactions and their respective enthalpy changes: III. III. C2H6(g) + 31/202(g) -> 2C02(g) + 3H20(I) C2H4(g) + 302(g) -> 2C02(g) + 2H20(I) 2H2(g) + 0 2 (g) -> 2H20(g) AH=-1560kJ AH = -1411kJ AH = -572kJ (3 marks)

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QUESTION 2 a) Carbon monoxide burns to form carbon dioxide according to...
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