CHEMISTRY 102 A/E Fall 2008 HOUR EXAM I NAME Dr. Christine Yerkes October 1, 2008 SIGNATURE Test Form A QUIZ TA A. DO NOT open the exam until you are instructed to do so. B. The exam has 6 pages. After you are instructed to begin the exam, please check to see that you have all of the pages. C. You should also have a list of helpful information and equations and a periodic table. D. The exam contains 26 questions. The point value of each question appears next to the question number. You have 75 minutes to complete the exam. E. Academic dishonesty. If cheating is observed, any student involved will receive a zero on the exam. INSTRUCTIONS FOR THE ANSWER SHEET 1. Use a soft lead pencil and make dark marks. Do NOT use a pen. Erase all changes completely. 2. Print your Name in the designated spaces, then blacken the letter boxes below each printed letter, last name first, then your first initial. 3. Under Network ID print your University Network ID starting from box #1, then blacken in the corresponding letters and numbers. 4. Sign your name (do not print) on the line provided. Your signature indicates that this is your work. Print your name underneath it. 5. Under Section use one of the following codes to signify your quiz section. AQ1 = 00001, AQ2 = 00002, AQ3 = 00003, AQ4 = 00004, AQ5 = 00005 AQ6 = 00006, AQ7 = 00007, AQ8 = 00008, AQ9 = 00009, AQA = 00010 AQB = 00011, AQC = 00012, AQJ = 00013 EQ1 = 00051, EQ2 = 00052, EQ3 = 00053, EQ4 = 00054, EQ5 = 00055 EQ6 = 00056, EQ7 = 00057, EQ8 = 00058, EQB = 00061, EQC = 00062 6. Mark only one answer for each question.
Solubility Rules: 1. Most nitrate salts are soluble. 2. Most salts of alkali metals and ammonium cations are soluble. 3. Most chloride, bromide and iodide salts are soluble. Exceptions: salts containing Ag +, Pb 2+ and Hg 2 2+ ions are insoluble 4. Most sulfate salts are soluble. Exceptions: sulfates containing Ca 2+, Ba 2+, Pb 2+ and Hg 2 2+ ions are insoluble 5. Most hydroxide salts are insoluble. Exceptions: hydroxides containing alkali metals, ammonium, Ba 2+, Sr 2+ and Ca 2+ ions are soluble 6. Most sulfide, carbonate, chromate and phosphate salts are insoluble. Exceptions: salts of alkali metals and ammonium cations are soluble Useful Constants and equations: K = o C + 273 M = Molarity = mol solute L solution PV = nrt % yield = actual yield x 100 theoretical yield R = 0.08206 L atm / mol K Avogadro's number = 6.022 x 10 23 STP = 1 atm, 273 K PM=dRT where d=density, M=molar mass 1 atm = 760 torr = 760 mm Hg d = density = mass/volume mass % of A = mass of A x 100 P 1 V 1 = P 2 V 2 total mass n 1 T 1 n 2 T 2
HE I page 1 1. (4) At 0 o C, 100.00 ml of a saturated solution of silver sulfate contains 0.57 g of dissolved silver sulfate. What is the concentration of silver ions in this solution? a) 0.0057 M b) 0.018 M c) 0.028 M d) 0.037 M e) 0.056 M 2. (4) Analysis of a compound yields the following percent composition by weight: 49.98% Ag, 24.09% Cr and 25.94% O. What is the empirical formula for this compound? a) Ag 2 CrO 4 b) Ag 2 Cr 2 O 7 c) Ag 2 CrO d) AgCrO 3.5 e) Ag 4 Cr 4 O 7 3. (3) The element dysprosium, Dy, forms an oxide with the formula Dy 2 O 3. The bromide of dysprosium will have the formula: a) Dy 2 Br 3 b) DyBr c) DyBr 2 d) DyBr 3 e) Dy 3 Br 2 4. (3) The ion X 3- has 36 electrons and an atomic mass of 70 amu. The element X is: element neutrons protons a) Ga 39 31 b) Ga 31 39 c) As 37 33 d) As 33 37 e) Kr 34 36 5. (4) When nitrogen monoxide is reacted with oxygen, the reddish-brown gas, nitrogen dioxide, is formed. How much nitrogen dioxide can be formed, when 3.823 grams of nitrogen monoxide and 2.886 grams of oxygen are mixed? a) 2.931 b) 4.149 c) 5.861 d) 6.709 e) 8.298
HE I page 2 6. (4) A solution of the sugar, fructose, in water is 20.0% fructose by weight and has a density of 1.082 g/ml. How many grams of fructose are in 45.00 ml of this solution? a) 4.869 g b) 9.738 g c) 48.69 g d) 97.38 g e) the formula of fructose is needed to answer this problem 7. (4) You add 250.0 ml of water to 10.0 ml of a solution of HI. The new concentration of HI is 0.380 M. What was the original concentration of HI? a) 0.0146 M b) 0.0152 M c) 0.380 M d) 9.50 M e) 9.88 M 8. (3) In the compound sodium oxalate, the molar ratio of sodium to carbon ions is: a) 1:1 b) 2:1 c) 1:2 d) 1:3 e) 2:3 Ethyl butyrate is the molecule that gives pineapples their distinctive odor. It contains 6 atoms of carbon per molecule. The weight percent of carbon in ethyl butyrate is 62.04%. Use this information to answer the next two (2) questions. 9. (4) What is the molecular weight of ethyl butyrate, in grams/mole? a) 19.30 b) 46.70 c) 100.16 d) 116.16 e) 4470 10. (4) When a 25.00 g sample of ethyl butyrate is burned with excess oxygen, 56.83 g of CO 2 and 23.26 g of H 2 O are produced. What is the formula of ethyl butyrate? a) C 3 H 6 O b) C 3 H 12 O 2 c) C 6 H 6 O 2 d) C 6 H 12 O 2 e) C 6 H 12
HE I page 3 11. (4) Which of the following is named incorrectly? a) K 3 P potassium phosphide b) K 3 PO 4 potassium phosphate c) CaO 2 calcium oxide d) CdCl 2 cadmium chloride e) CS 2 carbon disulfide 12. (4) A student dissolves 2.00 g each of CaCl 2, NaOH, (NH 4 ) 2 SO 4 and AgNO 3. How many different precipitates will form? a) 1 b) 2 c) 3 d) 4 e) 5 13. (4) When solutions of iron(iii) nitrate and sodium hydroxide are mixed, a red-brown precipitate of iron(iii) hydroxide is formed. Which of the following mixtures will produce the most of this precipitate? a) 10.00 ml of 0.100 M iron(iii) nitrate and 90.00 ml of 0.100 M sodium hydroxide b) 20.00 ml of 0.100 M iron(iii) nitrate and 80.00 ml of 0.100 M sodium hydroxide c) 25.00 ml of 0.100 M iron(iii) nitrate and 75.00 ml of 0.100 M sodium hydroxide d) 46.00 ml of 0.100 M iron(iii) nitrate and 54.00 ml of 0.100 M sodium hydroxide e) 64.00 ml of 0.100 M iron(iii) nitrate and 36.00 ml of 0.100 M sodium hydroxide
HE I page 4 Use the following substances to answer the next two (2) questions. I. (NH 4 ) 2 Cr 2 O 7 II. C 6 H 6 III. CH 3 CH 2 CH 2 OH IV. NH 3 V. H 2 C 2 O 4 14. (4) Which of the substances (I - V) will not dissolve in water? a) I b) II c) III d) IV e) V 15. (4) How many of these are strong, weak or non-electrolytes? strong electrolyte weak electrolyte non-electrolyte a) 1 1 3 b) 2 1 2 c) 1 2 2 d) 1 3 1 e) 0 3 2 16. (4) Methyl benzoate is prepared by the reaction between benzoic acid and methanol, as shown below: HC 7 H 5 O 2 + CH 3 OH C 8 H 8 O 2 + H 2 O benzoic acid methanol methyl benzoate In an experiment, 24.4 g of benzoic acid were reacted with 70.0 ml of methanol (density = 0.791 g/ml). The mass of methyl benzoate produced in this reaction was 21.6 g. What is the percent yield of the product? (The molecular weights are: benzoic acid = 122.1 g/mol, methanol = 32.0 g/mol, methyl benzoate = 136.1 g/mol) a) 91.7% b) 79.3% c) 71.5% d) 21.7% e) 9.17%
HE I page 5 17. (4) You dissolve 0.500 g of a solid, diprotic acid (H 2 A) in 100 ml of water. You titrate this solution with 0.150 M NaOH. It takes 29.7 ml of the 0.150 M NaOH to reach the equivalence point. What is the approximate molar mass of the acid? a) 11 g/mol b) 22 g/mol c) 56 g/mol d) 112 g/mol e) 224 g/mol 18. (4) What is the correct sequence of oxidation numbers for nitrogen in: N 2 NO 2 N 2 O 4 HNO 3 HNO 2 a) +1 +4 +2 +6 +4 b) 0-2 +4 +5 +5 c) 0 +4 +4 +5 +3 d) +1 +2 +4 +6 +4 e) none of these (a-d) are correct for this list of compounds 19. (3) How many of these nitrogen containing compounds can act as oxidizing agents? a) 1 b) 2 c) 3 d) all of them e) none of them Shown below is an unbalanced redox reaction. Balance it and use this information to answer the next three (3) questions. H 2 C 2 O 4 + NO 3 - CO 2 + NO 20. (4) What is the oxidizing agent? a) H 2 C 2 O 4 b) NO 3 - c) CO 2 d) NO e) H 2 O 21. (4) What is the oxidation state change for carbon? a) +6 +2 b) +4 +2 c) +2 +4 d) +5 +2 e) +3 +4 22. (4) What is the coefficient for water, in the balanced reaction? a) 0 b) 1 c) 2 d) 3 e) 4
HE I page 6 23. (4) A sample of gas at 35.0 o C and 1.00 atm occupies a volume of 3.75 L. At what temperature should the gas be kept if you want to reduce the volume to 3.00 L but keep the pressure constant? a) -26.6 o C b) 0.00 o C c) 3.98 o C d) 28.0 o C e) 112.0 o C 24. (4) A sample of pure gas has a density of 1.60 g/l at 26.5 o C and 680.2 mm Hg. Which of the following could be that gas? a) CH 4 b) PH 3 c) CO 2 d) Xe e) Xe 2 Cl 4 25. (4) A 1.7093 g sample of aluminum is reacted with excess aqueous hydrochloric acid to produce hydrogen gas: 2 Al (s) + 6 H + (aq) 3 H 2 (g) + 2 Al 3+ (aq) What volume of H 2 (g) is collected at a temperature of 24.8 o C and a pressure of 783.5 mm Hg? a) 2.946 ml b) 187.6 ml c) 1.502 L d) 2.129 L e) 2.258 L 26. (4) The density of lithium metal is 530 kg/m 3. What is its density in g/cm 3? a) 0.000530 b) 0.0530 c) 0.053 d) 0.53 e) 53.0