Exam 1D KEY

Exam 1D KEY - Name " E / (please print as name appears...

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Unformatted text preview: Name " E / (please print as name appears on UNC roll) Chemistry 101 Section 1 Seat rowl# Exam 1, September 17, 2010 Directions: I N l, \ 1. Print your name on the first and last pages of the exam. 2. For multiple-choice problems, write your answer (A, B, C, D, E) in the box provided on last page of exam. 3. On numerical problems, show your work including units as you go in order to receive credit for your work and write your answer in the box/line provided (include units). 4. Make sure your significant figures are correct. 5. Use pen or pencil, but only exams written in pen can be regraded. Honor pledge: l have neither given nor received help on this exam. Signed Worksheet D(H20) = 1.00 glmL 1 mL = 1 cm3 K= °C +273.15 D=M V Name " D (please print as name appears on UNC roll) Questions 1—5 (5 pts each): 1. What is the mass (in grams) of one molecule of F2? A) 35.0 \7 13) 2.29 x10:5 55-0 W o 1.58 x 10 2 H D 5.31 x 10'23 W _ q 4.37 x 10'26 5.022 x (025 mommies/moi 2. Chlorine (Z=17) has two stable isotopes with masses of 34.97 amu and 36.97 amu. What is the relative abundance of the two isotopes? - A) 50.00% 3501 and 50.00% 3701 0W5 a %-"W B) 54.55% 3501 and 35.45% 3701 c 35.45% 3501 and 64.55% 3701 @ 75.77% 3501 and 24.23% 3701 E) 24.23% 3501 and 75.77% 3701 3. There are 93 protons, 1 g neutrons, and electrons in an atom of 132Xe. A) 132, 132,54 Z'JW B) 54,54,132 C 78, 78, 54 54, 78, 54 ) 78, 78, 132 4. 3.337 kglma = 915m3 A 3.337x10‘g 43> 3.337 x 103 C) 3337 13) 0.3337 E) 33.37 5. When element X and element Y react to form an ionic compound, the tends to lose electrons and the tends to gain electrons. A) metal, metal B) nonmetal, nonmetal @ metal, nonmetal ) nonmetal, metal E) None of the above, these elements share electrons. Name ’- (please print as name appears on UNC roll) 7. Epicatechin, a healthy antioxidant in chocolate, is 33.07% oxygen, and every molecule contains 6 oxygen atoms. What is the molecular weight (in amu) of epicatechin? (6 pts) Wobblmasw smlamomssx (0239.. _ MW 8. Ascorbic acid, also known as Vitamin C, is present in chocolate. It has the following percent composition. What-is its empirical formula? (6 pts) ‘ %C=40.91 ! %H=4.578 40m Q‘ N..._____| = 3.4% ml Cal CH 36 % [2.0lcj %0=54.50 “(.619 HIWM '7 4.642 Wall—[#513396 4H 61 LODEc‘ '1' —-» l fat-Gog (15%; 8.4% mi 0x 0x \ V3 Ox 9. Combustion analysis of a 1.610 9 sample of equilin (containing only carbon, hydrogen, and oxygen) yields 4.753 g 002 and 1.081 9 H20. What is the empirical formuta of equiiin? (8 pts) CAL-NO;- v—“i‘ AWQBqCOz—i- (11851420 “clog i, *“ l-Z‘i‘l 05C .lOKD mi CD; .oesfifimi H20 -—- ,lzlg ll M23 ox .losoml O .lzoo‘W-H l; i, l/ H @ mg” C’ 420% dwdz mu metwr Maud b1 mum (M203 ‘Name (please print as name appears on UNC roll) 10. (10 pts) Name the following compound: CrPO4 - 2 H20 cumming lllh phosphate di’laydrale B_. Write the formula and name of the compound formed by the combination of calcium with nitrogen. Formula 02; N2 C. Write the name of 0102. Is this compound ionic or molecular? .H .l. .! Circte one: ionic 11. When nitrogen monoxide reacts with water, the reaction is as follows: 4NO+6H20~94NH3+502 A. When 0.125 mol NO and 0.140 mol H20 are ailowed to react, what is the composition (in mol) of the final mixture? (10 pts) LEE/Obtain: .129W10lMD‘4l/‘40‘NH5 = .129 mol 0H5 wtolND m3 INH ———— .Hovnolilofimw 3WD 5 Lies-'11:) 2 \omoleo .izipwitw emote =o.u‘+ mol 0; W .l4owoluo 4WMDuerol= mars WolMD z leleo 11$ch B. Suppose that only 0.085 mol NH3 are collected in the reaction. What is the percent yield of ammonia in this experiment? (2 pts) Name {3&er (please print as name appears on UNC roll) 6. The molecular formula for theobromine, the mood-enhancing ingredient in chocolate, is CTH10N402. A. What is its empirical formula? (2 pts) 6F: MP CEHQNfl 02.. B. What is the molecular weight of theobromine (in amu)? (4 pts) ‘4 (12.00 + to C l. 005) + 404-00 M 4- 6% 61.007 C. In 25 words or less, explain the number of sig figs you used to report your answer in 18. (4 pts) _ awe wasr accumfl Mass W 4?) thtdifispiace, 9cm W of Mass can bc Mpovwl +0 mm D. How many nitrogen atoms are in a 25 ug sample of theobromine? (6 pts) E. A 1.45-oz sewing of dark chocolate contains 184 mg of theobromine. How many moles of theobromine do | consume if I eat 5.00 oz chocolate bark for dessert? (6 pts) 6.000; “3ng \ moi L460; tall?) . .3 3 3.4% KID rmol SP F. When theobromine is combusted in the presence of oxygen, the products are carbon dioxide, water, and nitrogen dioxide. Write a balanced equation to represent this reaction- (6 pts) quwuLtoz + Zack—s H602+10HZO+ 8100; 3 Name -" (please print as name appears on UNC roll) 12. A piece of nickel foil, 0.550 mm thick and 1.45 cm square is allowed to react with excess hydrofluoric acid according to the following reaction: 2N1+2HF+2NiF2+H2 VN“: .OWOa/ndlflfiamoz What mass of hydrogen is produced? (8 pts) _ 6 D(Ni) = 8.91 glcma - . “(5%? 0M H)ng Ni lleNl l H7, 20% 5 141,5 Hz @6613 val NI WI 1 on? H 38F ' I 2 m n N ...
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This note was uploaded on 04/05/2012 for the course CHEM 101 taught by Professor Farahh during the Spring '02 term at UNC.

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Exam 1D KEY - Name " E / (please print as name appears...

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