exam2001 - Page 1 of 11 Queens University Faculty of...

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Page 1 of 11 Queen’s University Faculty of Applied Science APSC 132 Final Examination April 2001 YOUR NAME: ____________________ STUDENT NUMBER: ____________________ Time: three hours Only approved gold sticker calculators are admitted. Answer all questions in the space provided. Please put your student number and name in the space provided. NOT all questions are worth the same number of marks. The final page of this examination booklet contains a table of standard reduction potentials and the values of some constants. If doubt exists as to the interpretation of any question, you are urged to submit with your answer a clear statement of any assumptions made. The exam proctor may not be able to contact the instructor. QUESTION: 1 2 3 4 5 6 Total: MARKS: /60 HAND IN TEST PAPER
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Page 2 of 11 Thermodynamics Question #1 A system consists of a cylinder containing 10.0 L of an ideal gas at 25.0 o C at a pressure of 15.0 atm. The gas is allowed to expand against a constant opposing pressure of 5.0 atm until its pressure reaches 5.0 atm. Calculate the entropy changes in: (a) the system (b) the surroundings and (c) the universe for this process.
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Page 3 of 11 Acid and Base Chemistry Question #2 A solution is prepared by mixing 50 ml of 0.1M NaOH with 100 ml of 0.1M HA. HA is a weak acid with K a at 25 o C = 1.76 x 10 -5 . (a). Calculate the pH of the solution. (b). 25 ml of 0.1M HCl solution is added. Calculate the pH of the resulting solution. (c). Comment on the solution of (a) and the result of your calculation for part (b).
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Page 4 of 11 Electrochemistry Question #3 Aluminium has commercial potential as anode material in air batteries, i.e. batteries that use oxygen from air as the oxidizing agent. The electrolyte is a concentrated solution of KOH. The half reactions that take place are O 2 (g) + 2 H 2 O + 4 e - 4 OH - (aq) E 0 = 0.401 V [Al(OH) 4 ] - (aq) + 3 e - Al(s) + 4 OH - (aq) E 0 = -2.310 V {F = 96485 C/mol; M(Al) = 27g/mol} (a) Sketch a possible design of this battery, indicating cathode and anode, and the flow of electrons and ions. (3 points) Design with two "beakers" or with Al-electrode in an electrolyte solution is ok. If the design is wrong (electrodes missing, wire missing, saltbridge missing, etc) but the points below are correct do not give more than two points. Al-metal electrode is anode (oxidation) O 2 gas electrode is cathode (reduction) <1 point> electrons flow from Al to O 2 electrode <1 point> OH - flows the other way; K + flows the same way <1 point> (b) Calculate G 0 for the overall reaction at 25 0 C (2 points) G 0 = -nFE 0 = -12 96485C/mol (0.401+2.310)V = - 3138.8 kJ/mol n=12 <1 point> E 0 = 2.711V <1 point> no points if wrong equation is used Answer:
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