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Unformatted text preview: Chemistry 43 Midterm Examination Tuesday, 17 November 2009 N ame: _~_/)---,--5_Cd_er--_)U_ __ _ o Answer all questions completely and concisely. Give an explanation for all your answers. There are 6 questions on 11 pages worth a total of 100 points. You have 75 minutes in which to complete the exam. Write your answer in the space provided below the question; if there is insufficient room to do so, use the back of the page on which the question appears. For computational questions, please circle your final answer, taking care that it notes clearly units of measure where appropriate. In order to receive full credit for computational questions, all of your work must shown. All equilibrium problems on this exam are to be solved using methods detailed in your Chern 43 Course lectures; answers, for example, that derive from exact solutions to high order polynomial equations, will not be given full credit when simplifying assumptions could have been used to make the calculation in question more straightforward. Read the entire exam before beginning! 1. (20 points) Phosgene is a potent chemical warfare agent that is now outlawed by international agreement. It decomposes by the reaction COCl 2 (g) ~ CO (g) + Cl 2 (g) Kc = 8.3 X 10-4 (at 360 DC) Calculate [CO], [CI 2 ], and [COCI 2 ], when the following amounts of phosgene decompose and reach equilibrium in a 10.0-L flask: (a) 5.00 mol COCl 2 and (b) 0.100 mol COCl 2 o o ;( X x B [C CJ C I ~] -=- (J, ') - 0, 0 c. ::;: O,i..f 8' /?~ -- . ) - (6) Co C!2- .d= Co ..(/i,h-J 0 1 0 J 0hf'IJR -I e;j (J0 (J.G/-I- o x x -f C/2., o x ;r c;;mu..f.f) 0, 0 I --- ... _----- 2. (15 points) Sodium hypochlorite (NaOCl) is the active ingredient in laundry bleach. Typically, bleach contains 5% of this salt by mass, to provide a 0.67 M solution. Determine the concentrations of all species at equilibrium and compute the pH of laundry bleach....
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This note was uploaded on 09/19/2011 for the course CHEM 43L taught by Professor Therien during the Fall '09 term at Duke.
- Fall '09