Exam 1A KEY

Exam 1A KEY - Name ’Qéfi / (please print as name...

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Unformatted text preview: Name ’Qéfi / (please print as name appears on UNC roll) Chemistry 101 Section 1 Seat rowl# Exam 1, September 17, 2010 Directions: ‘3 /CW 3 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 boxlline 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 g/mL 1 mL = 1 cm3 K = °C + 273.15 Name K i ’_A'___ (please print as name appears on UNC roll) 1. The molecular formula for caffeine is CquoN402. A. What is its empirical formula? (2 pts) C4 111% Mg B. What is the molecular weight of caffeine (in amu)? (4 pts) 802.00 + lot L006) + Ll 04.00 + 7,099.00) ‘ lama“ becomes 9?.“ FifUE'EF C. in 25 words or less, explain the number of sig figs you used to report your answer 18. (4 pts) D. How many nitrogen atoms are in a 25 pg sample of caffeine? (6 pts) 23 96x15" mica? 4min (002le0 aims. [(414.2ch I wot Cal; 1 . H 6 (Q S F Wfilxiflm E. A 12-02 can of classic coca cola contains 34.0 mg of caffeine. How many moles o caffeine do i consume if i drink an 8-oz can of coke with lunch? (6 pts) ‘- ‘304 l W‘ = l. l'lx WW] r; 02: H4223 I 5x112“me l 1 SF beams 2K {0‘4 IMO! F. 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) x?“ ’r ' 0 acguwmol “‘7 ill/0902‘" 9521420 + L31“ 2 Name i “A (please print as name appears on UNC roll) 2. Fructose, the sweetening ingredient in coca cola, has the following percent composition. What is its empirical formula? (6 pts) %C=40.00 %H= 6.712 Afim [@003 ’Fwotosc: %O=53.29 0.00 C = Li 5% 3.633rmol c {onlch H = (o-lololp haul H L008? (fig-Q01 0 mol : 8333 Imole 3 vim" rug . 3. Tartrazine. a yellow food coloring, is yet another ingredient in coca cola. It is 12.91% sodium, and every molecule contains 3 atoms of sodium. What is the molecular weight (in amu) of tartrazine? (6 pts) 0M», was some (mama ae Ioo’z, MN MW fiammzmmx = Waww m 4. (10 pts) A. Name the following compound: CuSO4 - 2 H20 (other hydrated salt) LlDGul a ' ate, B. Write the formula and name of the compound formed by the combination of aluminum with sulfur. Formula mm; C. Write the name of P205. is this compound ionic or molecular? ' ow to' Circle one: ionic Name "' 2: (please print as name appears on UNC roll) 5. A piece of aluminum foil, measuring 11.45 cm x 5.10 cm x 0.611 mm, is reacted in excess hydrochloric acid according to the following balanced equation: 2Al+6HC|-)2AICI3+3H2 VM,=U.4‘5X5.|DX ODbllaMB What mass of hydrogen is produced? D(A|) = 2.70 glcm3 (8 pts) =7" 6 “ WU: 'D~ V’r A’L % A’L‘ Ntflz‘ Hz Flow? 2: 1.9581112 3 QIMDIAL 1mm 1 6. When ammonia undergoes combustion, the reaction is as follows: 4NH3+50294NO+6H20 A. When 0.125 mol NH3 and 0.150 mol 02 are allowed to react, what are the molar amounts of e B. Suppose that only 0.075 mol NO are collected in the reaction. What is the percent yield of NO in this experiment? (2 pts) Woniew .016 a [007° a @257, SF .l'zo (own) 4 Name "' A (please print as name appears on UNC roll) 7. Combustion analysis of a 1.893 9 sample of estrone, an organic compound containing only carbon, hydrogen, and oxygen (CxHyOz), yields 5.543 g 00; and 1.388 9 H20. What is the empirical formula of estrone? (8 pts) CLLHOB; -———~——7 6:456} Coz+ [-3883 “20 \l l; .1156! ml 00; .oarvroa mi H20 l \ .0141 Imol Ox [.6an 6 466213 l—l ’ H ' 0 Questions 8-12 (5 gts each): 8. 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 B) nonmetal, nonmetal C) metal, nonmetal D nonmetal, metal None of the above, these elements share electrons. 9. There are protons, neutrons, and electrons in an atom of E53Cu? & z (a 29, 34, 29 5 - B) 29, 29, 63 q o) 63, 29, 63 D) 29,29, 34 E) 34, 34, 29 10. What is the mass (in grams) of one molecule of methane, CH4? 1.04x10':: Q} 2.66 x 10' C) 3.76 x1022 “9.0an D) 9.64 x1024 \ E) 16.0 \I Ugo wot LDZZxIO” moltmlcs/ wwl Name 9 w A (please print as name appears on UNC roll) 11. Copper (Z=29) has two stable isotopes with masses of 62.97 amu and 64.90 amu. What is the relative aandance of the Wsotopes? I 69.95% u and 30.05% u MW ) 30.05% 35Cu and 69.95% 37Cu a I W C) 36.45% 3500 and 53.55% 37Cu D) 33.55% 3500 and 33.45% 37Cu E) 50.00% 350u and 50.00% 3700 12. 3.337 glcm3 = kglm3 A) 3.337x10’ 3 3.337 0‘3 7- 5, g) 337 x1 6.734% 3 [D - 3,3X ‘0 0.3337 E; 333.7 0’“ log 1M Question Answer Question Answer - [a (TO ...
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Exam 1A KEY - Name ’Qéfi / (please print as name...

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