exam - Chemistry 2740 Spring 2009 Final Examination Time: 3...

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Unformatted text preview: Chemistry 2740 Spring 2009 Final Examination Time: 3 hours Marks: 105 Aids allowed: calculator, 8 . 5 × 11-inch formula sheet Instructions: You can answer the questions in any order, but make sure that you clearly label each of your answers with the section and question number in your exam book- let(s). In questions whose answer requires the analysis of a graph, please sketch the graph. In section 2, you have a selection of questions. Do not answer more than the required number of questions. I will stop marking as soon as I have reached the required number of questions from this section. Extra answers will not be marked. If you answer extra questions, make sure you cross out the ones you don’t want me to mark. Data e = 1 . 60217646 × 10- 19 C F = 96485 . 342C / mol k B = 1 . 3806503 × 10- 23 J/K L = 6 . 0221420 × 10 23 mol- 1 R = 8 . 314472JK- 1 mol- 1 To convert degrees Celsius to Kelvin, add 273.15. Standard thermodynamic data at 298.15K Species Δ f H ◦ kJmol- 1 Δ f G ◦ kJmol- 1 C p,m JK- 1 mol- 1 F- (aq)- 335 . 35- 281 . 52 H 2 O (l)- 285 . 830- 237 . 140 75 . 40 SF 6(g)- 1220 . 47- 1116 . 44 96 . 88 SO 2- 4(aq)- 909 . 34- 744 . 00 Standard reduction potentials at 298.15K Reduction process E ◦ /V Cd 2+ (aq) + 2e- → Cd (s)- . 4030 Li + (aq) + e- → Li (s)- 3 . 0401 1 1 Answer all questions in this section. Value of this section: 85 marks 1. What is the first law of thermodynamics? [1 mark] 2. If we say, for a particular process on a particular system, that w =- 5J, what does that mean? [1 mark] 3. SF 6 is inert under most conditions. For example, it won’t undergo hydrolysis: SF 6(g) + 4H 2 O (l) 6→ 6F- (aq) + SO 2- 4(aq) + 8H + (aq) . Is the above reaction thermodynamically allowed at 25 ◦ C when the pressure of SF 6 is 0.2bar, the concentration of fluoride ions is 1 . × 10- 3 mol / L, the concentration of sulfate is 0.43mol/L, and the pH is 6.0? Does this agree or disagree with the empirical observation that SF 6 can’t be hydrolyzed? Discuss briefly. [7 marks] 4. Consider the following simple electrochemical cell: Cd (s) | CdCl 2(aq) (0 . 50mol / L) k LiCl (aq) (0 . 80mol / L) | Li (s) ....
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This note was uploaded on 03/03/2012 for the course CHEM 2740 taught by Professor Roussel during the Fall '07 term at Lethbridge College.

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exam - Chemistry 2740 Spring 2009 Final Examination Time: 3...

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