Chem 1711 Exam 1 September 26, 2013 Dr. Susan E. Bates Name 9:00 OR 10:00 N A = 6.022 x 10 23 mol 1 I A II A III B IV B V B VI B VII B VIII I B II B III A IV A V A VI A VII A inert gases 1 H 1.008 3 Li 6.941 11 Na 22.98 19 K 39.10 37 Rb 85.46 55 Cs 132.9 87 Fr (223) 4 Be 9.012 12 Mg 24.31 20 Ca 40.08 38 Sr 87.62 56 Ba 137.3 88 Ra 226.0 21 Sc 44.96 39 Y 88.91 57 * La 138.9 89 * Ac (227) 22 Ti 47.90 40 Zr 91.22 72 Hf 178.4 104 Rf (261) 23 V 50.94 41 Nb 92.91 73 Ta 180.9 105 Db (262) 24 Cr 52.00 42 Mo 95.94 74 W 183.8 106 Sg (263) 25 Mn 54.94 43 Tc 98.91 75 Re 186.2 107 Bh (262) 26 Fe 55.85 44 Ru 101.0 76 Os 190.2 108 Hs (265) 27 Co 58.93 45 Rh 102.9 77 Ir 192.2 109 Mt (266) 28 Ni 58.71 46 Pd 106.4 78 Pt 195.0 110 (269) 29 Cu 63.55 47 Ag 107.8 79 Au 196.9 111 (272) 30 Zn 65.37 48 Cd 112.4 80 Hg 200.5 112 (277) 5 B 10.81 13 Al 26.98 31 Ga 69.72 49 In 114.8 81 Tl 204.3 113? 6 C 12.01 14 Si 28.09 32 Ge 72.59 50 Sn 118.6 82 Pb 207.2 114 (289) 7 N 14.01 15 P 30.97 33 As 74.92 51 Sb 121.8 83 Bi 208.9 8 O 16.00 16 S 32.06 34 Se 78.96 52 Te 127.6 84 Po (210) 9 F 19.00 17 Cl 35.45 35 Br 79.90 53 I 126.9 85 At (210) 2 He 4.003 10 Ne 20.17 18 Ar 39.95 36 Kr 83.80 54 Xe 131.3 86 Rn (222) 58 Ce 140.1 90 Th 232.0 59 Pr 140.9 91 Pa (231) 60 Nd 144.2 92 U 238.0 61 Pm (147) 93 Np (237) 62 Sm 150.4 94 Pu (242) 63 Eu 151.9 95 Am (243) 64 Gd 157.3 96 Cm (247) 65 Tb 158.9 97 Bk (247) 66 Dy 162.5 98 Cf (251) 67 Ho 164.9 99 Es (254) 68 Er 167.3 100 Fm (253) 69 Tm 168.9 101 Md (256) 70 Yb 173.0 102 No (254) 71 Lu 174.9 103 Lr (257)
Chem 1711: Exam 1 Part I (46 points): Short Answer. Name 1. Give the missing IUPAC name or chemical formula for each of the following: FeBr 2 4H 2 O nickel (III) hydroxide IF 5 yttrium chlorite HC 2 H 3 O 2 (aq) dinitrogen tetroxide 2. a. Give the name of one transition metal found in the 5 th period of the periodic table. b. Give the name of one metalloid in group VA of the periodic table. c. Consider the element with 19 protons in its nucleus. This element is best described as which one of the following? halogen noble gas alkali metal alkaline earth metal 3. Consider the ion 121 Sn 2+. How many protons, neutrons & electrons are there? p n e 4. Balance the following chemical equation: IBr + NH 3 NI 3 + NH 4 Br 5. a. Consider 65 molecules of P 2 O 5. This collection of molecules contains how many phosophorus atoms? How many atoms in total are contained in this sample? b. A 0.200 mol sample of P 2 O 5 contains how many molecules? c. What is the mass of 1 P 2 O 5 molecule? Circle the one best answer below. 46.97 amu 46.97 g 111.0 amu 111.0 g 141.9 amu 141.9 g 6. a. Which of the following numbers has (unambiguously) 4 significant figures? Circle the one best answer below: 7000 0.005080 3.0 x 10 3 10.130 4.41 x 10 4 b. Give the answer to the following calculation with the correct number of significant figures: 0.17 0.00860 6.710 + 4.859 = 7. 32 molecules of NH 3 and 35 molecules of O 2 are combined and allowed to react accoring to the following equation: 4 NH 3 (g) + 5 O 2 (g) 4 NO (g) + 6 H 2 O (g) a. Identify the limiting reactant. b. What is the maximum number of water molecules that can form? c. How many molecules of the excess reactant remain unconsumed when the reaction is complete?
8. Perform the following unit conversions: a. 26.2 lb/in 2 = kg/m 2 b. 675.9 kj = MJ 1 lb = 453.59 g; 1 in = 2.54 cm 9. A 750 g sample of a compound composed of only manganese and oxygen is analyzed and found to contain 210 g O. Determine the mass percent manganese in this compound. Part II (39 points): Multiple Choice. For each of the following questions, indicate the one best answer by bubbling in the appropriate letter on the provided Scan Tron answer sheet. 1. Calculate the average atomic mass for fictional element El given the following data: symbol isotope mass percent abundance 121 El 121.943 amu 16.26 124 El 124.009 amu 19.57 125 El 124.981 amu 64.17 a. 123.6 amu b. 124.3 amu c. 125.0 amu d. 124.5 amu e. 80.20 amu 2. Who is credited with establishing the nuclear structure of the atom? a. J.J. Thomson b. Joseph Proust c. John Dalton d. Ernest Rutherford e. Antoine Lavoisier 3. Which one of the following statements about isotopes of a particular element is not true? a. Each unique isotope has a different atomic mass. b. Each unique isotope has a different atomic number. c. Each unique isotope has a different number of neutrons. d. Each unique isotope has a different number of nucleons. e. In neutral atoms of each isotope, the number of electrons equals the number of protons. 4. The term that is related to the reproducability of a measurement is a. precision b. accuracy c. qualitative d. intensive e. physical 5. A 0.8650 g sample of an element contains 5.062 x 10 21 atoms. Identify this element. a. I b. Ag c. La d. Pd e. Rh
6. A 19.0 g sample of lithium is burned in air and converted completely to lithium oxide. The mass of lithium oxide formed must be a. exactly 19.0 g b. less than 19.0 g c. more than 19.0 g d. equal to 30.0 g e. there is not enough information provided to answer this question 7. Which of the following are binary molecular compounds? i. C 5 H 10 ii. HNO 2 iii. Al 2 O 3 iv. Cl 2 O 7 v. Na 3 PO 4 a. i, iii, iv b. i, ii, iv c. ii, iii, v d. i and iv e. none of these 8. Which one of the following is the greatest? a. number of nitrogen atoms in 1 mol of ntirogen in its elemental form b. number of formula units in 1 mol of ammonium phosphate c. number of ammonium ions in 1 mol of ammonium phosphate d. number of oxygen atoms in 1 mol of ammonium phosphate e. number of molecules in 1 mol of nitrogen dioxide 9. A compound has C 3 H 5 O 2 as its empirical formula. Which one of the following can not be this compound s molecular formula? a. C 3 H 5 O 2 b. C 9 H 10 O 6 c. C 12 H 20 O 8 d. C 6 H 10 O 4 e. all of these are possible 10. Consider the following reaction: I 2 (s) + 2 Na 2 S 2 O 3 (aq) Na 2 S 4 O 6 (aq) + 2 NaI (aq). Determine the mass (in g) of I 2 required to react completely with 10.97 g Na 2 S 2 O 3. For I 2, molar mass = 253.8 g/mol; for Na 2 S 2 O 3, molar mass = 158.1 g/mol. a. 8.805 g b. 17.61 g c. 35.22 g d. 16.05 g e. 5.485 g 11. Calculate the density (in g/cm 3 ) of technetium if 0.246 mol occupies a volume of 2.11 cm 3. a. 24.3 g/cm 3 b. 8.58 g/cm 3 c. 46.9 g/cm 3 d. 0.519 g/cm 3 e. 11.5 g/cm 3 12. Which one of the following statements about lab measurements is correct? a. A 50-mL burette is not as precise as a 50-mL graduated cylinder. b. Extrapolation is a more reliable method of estimation than interpolation. c. In a linear graph of time vs. distance, the slope can have units of cm/s. d. Standard deviation is an indication of the accuracy of a set of measurements. e. A 25-mL pipette is precise to 4 significant figures.
13. Based on the observaitons you made during the Reactions and Solubility lab, which one of the following ions is generally not soluble? a. Na + b. K + c. NH 4 + d. Ag + e. NO 3 Part III (15 points): Problems. Work each of the following problems. Show all work clearly; work with units in all steps; report your answers with correct units and significant figures. No partial credit will be given if I cannot follow your work. 1. A compound is composed of potassium, chromium, and oxygen. After analysis, it is found to be 26.58 % potassium and 35.35% chromium by mass. Determine the empirical formula of this compound. 2. Consider saccharin (C 7 H 5 NO 3 S) to answer a c below. a. Determine the molar mass of saccharin. Include units with your answer. b. Determine the amount (in mol) of saccharin that contains 2.8 x 10 12 carbon atoms. mol c. Determine the mass (in g) of oxygen in 825 mg saccharin. g 3. Consider the following reaction: Fe 3 O 4 (s) + 4 H 2 (g) 3 Fe (s) + 4 H 2 O (l) 1.000 kg Fe 3 O 4 and 500.0 g H 2 are combined and allowed to react. Determine the mass (in g) of iron collected if the reaction proceeds in 88.22% yield. g