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UL Lafayette CHEM 107 - EXAM 1 - CHEM 107

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1CHEM 107 (Fall-2006) Exam 1 (104 pts) Name: ------------------------------------------------------------------------, Clid # ------------------------------- LAST NAME, First (Circle the alphabet segment of your LAST NAME): A-C D-H I-L M-O P-Z Please answer the following questions: Part I: Multiple Choices (48 pts: 12 @ 4 pts each + 4 pts bonus). Circle the ONE best answer: 1. An atom containing 34 protons, 43 neutrons, and 34 electrons would have the symbol: a) 77Se b) 77Ir c) 43Se d) 43Tc 2. Oxygen is the third most abundant element in the universe and makes up about two thirds of the human body. Which of the following statements is classified as an extensive property? a) Liquid oxygen boils at 90.2 K. b) Liquid oxygen is pale blue. c) Oxygen has a density of 1.43 g/L at 0º C. d) A volume of 22.4 L of oxygen gas weighs 32 g 0º C. 3. Perform the indicated operations and give the answer in cm with the proper number of significant figures. (28.1 cm – 5.30 mm + 0.75321 m)/(5.0 cm) = ? a) 20.8 b) 6.8 c) 21 d) none of the above 4. Which name is incorrect? a) Mg(NO3)2: magnesium nitrate b) CoSO4: cobalt(II) sulfate c) Fe2S3: diiron trisulfide d) S2F4: disulfur tetrafluoride 5. Predict the product of the reaction of gallium, Ga with selenium, Se. a) Ga2Se3 b) Ga3Se2 c) GaSe2 d) Ga2Se2 6. Which of the following statements is incorrect? a) A proton carries a +1 charge and an electron carries -1 charge. b) A neutron is an uncharged particle with a mass slightly greater than a proton. c) More than 99.9% of an atom’s mass is concentrated in the nucleus in which protons and neutrons are located. d) None of the above2 7. Naturally occurring neon consists of two isotopes Ne-20 and Ne-22. The atomic mass of Ne is approximately 20.2. What are the reasonable estimates of the relative percentages of Ne-20 and Ne-22, respectively? a) 10, 90 b) 90, 10 c) 80, 20 d) 50, 50 8. How many electrons, protons, and neutrons are found in a 208Pb2+ ion? a) 82 electrons, 82 protons, 126 neutrons b) 80 electrons, 82 protons, 126 neutrons c) 84 electrons, 82 protons, 126 neutrons d) 80 electrons, 82 protons, 46 neutrons 9. What is the number of moles of Br2 that contain 6.022 x 1021 molecules of Br2? a) 0.01 b) 3.768 x 1019 c) 1.598 d) no answer was given 10. Calculate the percent of nitrogen by mass in ammonium nitrate. a) 35 b) 17.5 c) 22 d) no answer was given 11. What mass of phosphorus trichloride, PCl3 in grams that can be made from 35.0 g Cl2 (g) according to the following equation? 2 P (s) + 3 Cl2 (g) 2 PCl3 (l) a) 45.2 b) 67.8 c) 90.4 d) 15.1 12. Which of the following could be a simplest formula? a) N2O4 b) N2 c) C6H5Br d) C6H3F3 13. (Bonus: 4 pts) When 0.225 mol butane, C4H10, is burned with excess oxygen how many molecules of oxygen are consumed? 2 C4H10 (g) + 13 O2 (g) 8 CO2 (g) + 10 H2O (l) a) 1.46 b) 8.87 x 1023 c) 5.42 x 1023 d) no answer was given3Part II. Names, formulas and properties (28 pts: 14 @ 2 pts each) – NO Partial Credits 1. (16 pts) Complete the following table with the formula or the name of the compound Name Formula Cu(NO3)2 Chromium(III) oxide Magnesium nitride Phosphoric acid Fe3(PO4)2 S2F4 Potassium chlorate HBr (g) 2. (12 pts) Consider the following substances: SO3, XeOF4, N2, ScCl3, AsCl3, NiSO4 and NO2. a) Which are diatomic? ------------------------------------ b) Which are ionic? ------------------------------------ c) Which are molecular (covalent)? ------------------------------------ d) Which compound is derived from a noble gas? ------------------------------------ e) Which compound(s) is derived from a transition metal? ------------------------------------ f) Which compound is derived from a metalloid element? ------------------------------------- Part III. Calculations (24 pts): Show all work for full credit. Please express all answers with the proper units and correct number of significant figures. 1. (8 pts) Copper (Cu), an excellent conductor of heat is composed of two isotopes. One of the isotopes has an atomic mass of 62.9208 amu and 69.09 % abundance. What is the atomic mass of the other isotope and what is its mass number? Atomic mass: 64.9278 Mass number: 6542. (16 pts) Caffeine is the compound that found in coffee, tea, and cola drinks and has a marked stimulatory effect on mammals. Chemical analysis of caffeine shows that it contains 49.38% C, 5.26% H, 28.76% N, and 16.60% O by mass, and its experimentally determined molar mass is 196 g/mol. Calculate: a) the simplest formula and b) the molecular formula of caffeine a) Simplest formula C4H5N2O b) Molecular formula C8H10N4O25 Exam 1 – Fall 2006 You will have 50 minutes to complete this exam. The exam has 4 pages plus the Periodic Table Reference page. When you are told to do so, tear off the Periodic Table cover sheet and use as required during the exam. 1. 1 1 H 1.01 Periodic Table of the Elements 2 He 4.00 2 3 Li 6.94 4 Be 9.01 5 B 10.816 C 12.01 7 N 14.01 8 O 16.009 F 19.0010 Ne 20.18 3 11 Na 22.99 12 Mg 24.30 13 Al 26.9814 Si 28.08 15 P 30.97 16 S 32.0617 Cl 35.4518 Ar 39.95 4 19 K 39.1 20 Ca 40.08 21 Sc 44.96 22 Ti 47.8823 V 50.94 24 Cr 52.00 25 Mn54.9426 Fe 55.8527 Co 58.9328 Ni 58.6929 Cu 63.5530 Zn 65.3831 Ga 69.7232 Ge 72.59 33 As 74.92 34 Se 78.9635 Br 79.9036 Kr 83.80 5 37 Rb 85.47 38 Sr 87.62 39 Y 88.91 40 Zr 91.2241 Nb 92.91 42 Mo 95.94 43 Tc (98) 44 Ru 101.145 Rh 102.946 Pd 106.447 Ag 107.948 Cd 112.449 In 114.850 Sn 118.7 51 Sb 121.8 52 Te 127.653 I 126.954 Xe 131.1 6 55 Cs 132.9 56 Ba 137.3 57 La 138.9 72 Hf 178.573 Ta 181.0 74 W 183.8 75 Re 186.276 Os 190.277 Ir 192.278 Pt 195.179 Au 197.080 Hg 200.681 Tl 204.482 Pb 207.2 83 Bi 209.0 84 Po (209) 85 At (210) 86 Rn (222) 7 87 Fr (223) 88 Ra 226.0 89 Ac 227.0 104 Rf (261) 105 Db (262) 106 Sg (263) 107 Bh (262) 108 Hs (265) 109 Mt (266) 110 Uun(269) 111 Uuu(272) 112 Uub(277) 58 Ce 140.159 Pr 140.9 60 Nd 144.2 61 Pm(145) 62 Sm 150.463 Eu 152.064 Gd 157.265 Tb 158.966 Dy 162.567 Ho


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