t3a - Wednesday, November 17, 2004 11:05 a.m. - 11:55 a.m....

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3.091 Fall Term 2004 Test #3A Wednesday, November 17, 2004 11:05 a.m. - 11:55 a.m. N a m e : (please print in UPPER CASE) Recitation Instructor: A complete test consists of 4 questions. Write your answers on these pages. State your assumptions and show calculations that support your conclusions. RESOURCES PERMITTED: PERIODIC TABLE OF THE ELEMENTS, TABLE OF CONSTANTS, AN AID SHEET (ONE PAGE 8½" × 11"), AND A CALCULATOR. NO BOOKS OR OTHER NOTES ALLOWED. USE OF WIRELESS COMMUNICATIONS DEVICES STRICTLY FORBIDDEN. #1 24% #2 28% #3 28% #4 20% TOTAL 100%
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3.091 Fall Term 2004 Test #3A page 2 Problem #1 (24%) log 10 (rate) catalyzed reaction slope, n = 2 intercept, k = 3.091 log 10 (concentration) The fictitious compound, pandemonium fluoride (Pd 2 F 3 ), decomposes readily at temperatures exceeding 765ºC. The figure above shows the kinetics of the reaction conducted at 800ºC. The reaction is second –1 order in concentration of Pd 2 F 3 . The value of the specific chemical rate constant, k , is 3.091 L mol –1 s . 4% (a) On the graph above, label the slope and the intercept, indicating the numerical value of each. (b) Calculate how long it takes at 800ºC for the concentration of Pd 2 F 3 to fall from 1.11 mole L –1 to 10% of that value. Express your answer in seconds. 14% (c) The same reaction is now conducted under the influence of a catalyst. On the graph above, which shows the reaction as it proceeds in the absence of a catalyst, draw the line associated with the catalyzed reaction. 6% Problem #2 (28%)
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3.091 Fall Term 2004 Test #3A page 3 Composition A: 5% MgO – 95% SiO 2 ; Composition B: 20% MgO – 80% SiO 2 (a) Two glass-forming melts, A and B as specified above, are each cooled at the same rate down to room temperature. Identify which melt, A or B, exhibits the higher glass transition temperature and explain why. 8%
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t3a - Wednesday, November 17, 2004 11:05 a.m. - 11:55 a.m....

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