101E2_2006key

101E2_2006key - Chemistry 101 Examination 2(A), June 16,...

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Chemistry 101 Examination 2(A), June 16, 2006 page 1 of 10 PRINT NAME______________________________ SIGNATURE_________________________ Last First Recitation Instructor_________________ There is 1 question in Part I and 18 multiple choice questions in Part II, in addition to one page of equations and a Periodic Table with constants, for a total of 10 pages . Be sure you have a complete copy before you begin. The backs of pages 3-11 can be used as scrap paper. Turn in pages 1 and 2. Part I. Answer each question in the space provided on the page. You must show your work for credit. Part II: For each question choose the one best answer. Indicate the letter corresponding to this answer in the proper space in the box to the left. It is best to use pencil and erase completely any answers you want to change. Questions with more than one answer marked will be graded as incorrect. Do not leave any answers blank - guess if you don't know. Part I __________(10) Part II __________(90) Total __________(100) version A A B C D E % correct 2 x 48% 3 x 63% 4 x 81% 5 x 41% 6 x 67% 7 x 67% 8 x 65% 9 x 44% 10 x 76% 11 x 61% 12 x 43% 13 x 33% 14 x 26% 15 x 46% 16 x 41% 17 x 31% 18 x 33% 19 x 56% A B C D E
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Chemistry 101 Examination 2(A), June 16, 2006 page 2 of 10 Part I. NAME______________________________ 1. (10 points) When 50.0 mL of 0.400 M Ca(OH) 2 (aq) is added to 50.0 mL of 0.400 M H 3 PO 4 (aq), a precipitate of Ca 3 (PO 4 ) 2 (s) forms. The balanced equation is below. ΔH for this reaction is -83.35 kJ/mol. The initial temperature of both solutions is 25.0 ° C. What is the final solution temperature, assuming the total mass is 100.0 g and the specific heat of the final solution is 4.18 J/g- ° C? 2 H 3 PO 4 (aq) + 3 Ca(OH) 2 (aq) Ca 3 (PO 4 ) 2 (s) + 3 H 2 O(l) ΔH = -83.35 kJ/mol. Ca(OH) 2 is limiting reagent 1 point (0.0500 L)(0.400 M Ca(OH) 2 )(1 mol reaction/3 mol Ca(OH) 2 ) = 6.67x10 -3 mol reaction 2 points (6.67x10 -3 mol reaction)(-83.35 J/mol)(1000 J/kJ) = -556 J 3 points q solution = -q reaction = +556 J = (100.0 g)(4.18 J/C-g)(T-25.0 C) 4 points T = 26.3 ° C 1 point
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Chemistry 101 Examination 2(A), June 16, 2006 page 3 of 10 Part II. Each question is worth 5 points.
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101E2_2006key - Chemistry 101 Examination 2(A), June 16,...

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