Exam 1C KEY

Exam 1C KEY - _Seat rowl Name 4(please print as name...

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Unformatted text preview: _Seat rowl# Name 4 (please print as name appears on UNC roll) Chemistry 101 Section 1 Exam 1, September 17, 2010 Directions: 1. 2. 3. 9"? Print your name on the first and last pages of the exam. Wg’ For multiple—choice problems, write your answer (A, B, C, D, E) in the box provided on last page of exam. 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). Make sure your significant figures are correct. 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 g/mL 1 mL =1 cm3 K=°C 0:14 V + 273.15 Name i< 14c. (please print as name appears on UNC roll) Questions 1-5 5 ts each : 1. Copper (2:29) has two stable isotopes with masses of 62.97 amu and 64.90 amu. What is the relative abundance of the two isotopes? @69.95% 3500 and 30.05% 37Cu (1)13 1: [93 -%O,mu, 30.05% 35Cu and 69.95% 37Cu O) 36.45% 35Cu and 63.55% 37Cu D) 63.55% 350u and 36.45% 37Cu E) 50.00% 35Cu and 50.00% 37Cu 2. When element X and element Y react to form a molecular compound, the tends to lose electrons and the tends to gain electrons. A) metal, metal 3) nonmetal, nonmetal 0) metal, nonmetal D) nonmetal, metal 65) None of the above, these elements share electrons. 3. There are Zq electrons, protons, and neutrons in an atom of 63Cu? (9 ' <5) 29, 29, 34 2; B) 29,29, 63 ___.. 0) 63,29, 63 54 D) 34,29, 34 E) 34, 34, 29 4. What is the mass (in grams) of one molecule of methane, CH4? A) 1.04 x 10'25 B) 9.64x1024 [[0 fly..— ll -23 ) i 1322 Wt [6.0223l073molecules E) 16.0 5. 3.337 g/cm3 = kg/m3 A) 3.337 x 10'5 B) 3.337 x10‘3 2 5 $33373, 7,2531 k “3va = 7533451 E) 333.7 QM? “>63 MA )MB Name "‘ (please print as name appears on UNC roll) 6. (10 pts) A. Name the following compound: Ni(N03)2 - 4 H20 his '++ afi'C B. Write the formula and name of the compound formed by the combination of magnesium with nitrogen; Formula Mgr im m’nr C. Write the name of P2H5. Is this compound ionic or molecular? W Circle one: ionic 7. A piece of aluminum foil, measuring 11.45 cm x 5.10 cm x 0.511 mm, is reacted in excess hydrochloric acid according to the following balanced equation: 3 2 Al + 6 Ho] 9 2 moi + 3 H2 VA; [L45 x 6.le 0.051 lcm What mass of hydrogen is produced? D(AI) s 2.70 gl’cm3 (8 pts) '5 2 C1443 MN} 9- Vc 8-003 8.003sz 902,3 ng 2mm. W 2. SF 8. Combustion analysis of a 1.342 9 sample of estradiol (containing only carbon, hydrogen, and oxygen) yields 3.901 g 002 and 1.065 9 H20. What is the empirical formula of estradiol? (8 pts) Ufl'l ,\ ..« LO!» [ .088Ulmol0 .ll‘SZmol Hi .. .iiq i, “A, l) .lHlflH .i%30K 1.01063 C Olivia; Val .DOQSS: -C0q88mole - 3 QC: 12H: I01: Name K I'" (please print as name appears on UNC roll) 9. When ammonia undergoes combustion, the reaction is as follows: 4NH3+502—)4NO+6H20 A. When 0.125 mol NH3 and 0.145 mol 02 are allowed to react, what are the molar amounts of each substance present after the reaction is complete? (10 pts) l L“ WW mol N .lZGvnol 1W 4W woe . 126ml no m u%%b 34zggmg cal-uni- ___,,.lllv;wmloz 14m: no g .1“; mi N0 6W 02 .l‘leolO [4moIMH3 .l‘lfi mol FE 0: .Fl‘l Imol l-lLO z GmoIOz z =. lilo Imol Allis (12d B. Suppose that only 0.070 mol NO are collected in the reaction. What is the percent yield of NO in this experiment? (2 pts) 3 . = . l 620 “’K 9° .llla Moi or (00.075 10. The molecular formula for caffeine is C3H10N402. A. What is its empirical formula? (2 pts) Cfl Hfiuzo B. What is the molecular weight of caffeine (in amu)? (4 pts) 8(n00 + lb ( l .008) + 4K (4 .00 C. In 25 words or less, explain the number of sig figs you used to report your answer in 18. (4 pts) 41> Least si'q w‘fiawul- dccld'd'vém u as 0 , mi? Mummers (110(wa pfa Name -" C (please print as name appears on UNC roll) D. When caffeine 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) 2C3HioNtiOz+ljr02 ———-v upcoz+ [0420+ 8in2 E. How many oxygen atoms are in a 25 pg sample of caffeine? (6 pts) F. A 12-02 can of classic coke contains 34.0 mg of caffeine. How many moles of caffeine do I consume if I drink a 20-02 bottle of coke with lunch? (6 pts) 10 012W I [202: H4223 04 l [SF uu 5M lax to'iml 11. Tartrazine, a yellow food coloring, is yet another ingr ient in coca cola. It is 12.71% sodium, and every molecule contains 3 atoms of sodium. What is the molecular weight (in amu) of tartrazine? (6 pts) WWW wa‘ * MW: (4; mammal am)-ioo?, = 6421, W “P Name \{E " (please print as name appears on UNC roll) 12. Fructose, the sweetening ingredient in coke, has the following percent composition. What is its empirical formula? (6 pts) %C=40.00 %H= 6.712 %O=53.29 taillsz l = We ml H [.0083 CH O '57) ZQjOX ‘ = 3 33 [Mel Ox [(9.003 Answer 4 n- 5 . -ra- i ...
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Exam 1C KEY - _Seat rowl Name 4(please print as name...

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