F2021 Exam 2 KEY for posting

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Vanderbilt University *

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1601

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Chemistry

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Apr 3, 2024

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pdf

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Uploaded by SuperDinosaurMaster401

1 ©T.Todd, S.Phillips, C.Tainter, A.List, A.Daniel Students do not have permission to post this to ANY external website, nor share via any electronic medium. CHEM 1601 – FALL 2021 Examination 2 Instructions: 1) Turn your phone off. Place your phone either in your pocket or under your desk. 2) PRINT your name on the upper left-hand side of every page of the Answer Sheet, in the appropriate box. Circle the section in which you are enrolled. 3) No phones , books, notes, or any other devices (AppleWatches, FitBits, Tablets, etc. that can send and receive texts and data or access the internet) are allowed during the exam. 4) There should be no data stored in your calculator, including but not limited to, Periodic Tables, chemical equations, or formulas. 5) There are 28 problems in 5 sections on 8 total pages including the coversheet and Data Sheet. The Answer Sheet is a separate document, and is 4 pages in length. 6) Be certain that, whenever applicable, show your work and include all relevant units. Problems answered without showing work will receive no credit (section 1). 7) Write your final answers clearly and legibly in the box provided. Answers not clearly written or ambiguous answers will be marked wrong. Only work inside the provided area will be graded. Do not write answers outside of the supplied boxes. Work written anywhere else will not be graded. 8) Do not include any separate pages of extra work. 9) Be certain to read each problem carefully! No question is written be intentionally misleading. 10) If you have a question, please ask your proctor.

2 ©T.Todd, S.Phillips, C.Tainter, A.List, A.Daniel Students do not have permission to post this to ANY external website, nor share via any electronic medium. Section 1. Calculations. (28 pts) In this section you must show all work for full credit , including units where appropriate. Answers without work shown will receive no credit . Only work inside the box labeled “Work” on the answer sheet will be graded for partial credit. Your answer should be written in the boxes labeled “Answers” on the answer sheet. Keep in mind, you may not have enough time to transfer work and answers to the Answer Sheet. 1. Citric acid (C 6 H 8 O 7 ) is produced by the oxidation of sucrose (C 12 H 22 O 11 ) in the presence of oxygen, as shown by the following equation: C 12 H 22 O 11 (aq) + 3 O 2 (g) à 2 C 6 H 8 O 7 (aq) + 3 H 2 O( l ) The average 750 mL bottle of port wine has a density of 1.085 g/mL, and is 11.1% sucrose by mass. After the bottle of port has been open to the atmosphere for several days, a vintner measured the citric acid content and found that there is an average of 55.6 g of citric acid per bottle. What percent of the sucrose (on average) was converted to citric acid per bottle of port wine? (MW sucrose = 342.297 g/mol; MW citric acid = 192.123 g/mol) (7 pts)

3 ©T.Todd, S.Phillips, C.Tainter, A.List, A.Daniel Students do not have permission to post this to ANY external website, nor share via any electronic medium. 2. Bebeerine, an organic compound containing C, H, N, and O, is commonly employed as an antimalarial. Antimalarials can be effective against fevers and sweating, both common symptoms of taking CHEM 1601 exams. A bebeerine sample of mass 4.732 g consumed 11.331 g of oxygen when burned. The products of the reaction were 12.609 g of CO 2 (44.01 g/mol), 2.724 g of H 2 O (18.0 g/mol), and 0.732 g of NO 2 (46.01 g/mol, all N in bebeerine forms NO 2 during combustion). The molar mass of bebeerine is 594.68 g/mol . (12 pts) a. Calculate the mass of oxygen in the bebeerine sample. b. Determine the molecular formula of bebeerine. c. Write out a balanced chemical reaction for the combustion of bebeerine based on the formula you calculated in part (b)

4 ©T.Todd, S.Phillips, C.Tainter, A.List, A.Daniel Students do not have permission to post this to ANY external website, nor share via any electronic medium. 3. Barium Oxide (BaO) in the gas phase has a dipole moment of 7.95 D. The Ba-O bond length is 203.1 pm. If the % ionic character of BaO (g) is 40.8 % what is the actual value of the number of electron(s) transferred from Ba to O in the gas phase compound? (4 pts) There are two methods 1) Using dipole moment equation ࠵? = ࠵? ∙ ࠵? ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵?࠵?࠵?. ࠵?࠵?࠵?࠵?࠵? ࠵? = ࠵? ࠵? = (7.95 ࠵?) 5 3.34 × 10 ;<= ࠵? ∙ ࠵? 1 ࠵? @ 203.1 × 10 ;BC ࠵? = 1.307 × 10 ;BD ࠵? ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵? ࠵?࠵?࠵?࠵? ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵?࠵? ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?. ࠵? = (1.307 × 10 ;BD ࠵?) 5 1 ࠵? ; 1.60 × 10 ;BD ࠵? @ = 0.817 ࠵? ; Or 2) Using the %ionic character equation %࠵?࠵?࠵?࠵?࠵? ࠵?ℎ࠵?࠵?࠵?࠵?࠵?࠵?࠵? = 100% 5 ࠵?࠵?࠵?࠵?࠵?࠵? ࠵?࠵?࠵?࠵?࠵?࠵? ࠵?ℎ࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵?࠵? ࠵?࠵?࠵?࠵?࠵? ࠵?࠵?࠵?࠵?࠵?࠵? @ = 100% 5 ࠵? RSTURV ∙ ࠵? ࠵? TWXYZ ∙ ࠵? @ The bond length (r) cancels. Also q is the #of electrons transferred * charge (in C) per electron. % ࠵?࠵?࠵?࠵?࠵? ࠵?ℎ࠵?࠵?࠵?࠵?࠵?࠵?࠵? = 100% [ (#࠵? RSTURV ; ) ]1.60 × 10 ;BD ࠵? ࠵? ^ (#࠵? TWXYZ ; ) ]1.60 × 10 ;BD ࠵? ࠵? ^ _ The theoretical number of electrons transferred in BaO is 2 electrons to make Ba 2+ and O 2- . 40.8% = 100% 5 #࠵? RSTURV ; 2 ࠵? ; @ 0.408 ∙ 2࠵? ; = #࠵? RSTURV ; #࠵? RSTURV ; = 0.816 ࠵? ; 4. Potassium nitrate is used as a common fertilizer. It is produced by the reaction of aqueous postassium chloride with nitric acid and oxygen gas. Additional products include chlorine gas and water. Write a balanced chemical equation for the production of aqueous potassium nitrate. (5 pts) 4 KCl (aq) + 4 HNO 3 (aq) + O 2 (g) 4 KNO 3 (aq ) + 2 Cl 2 (g) + 2 H 2 O (l)

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