16-exam1 - CHEMISTRY 16 EXAM I Dr M Richards-Babb July 9...

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Unformatted text preview: CHEMISTRY 16 EXAM I Dr. M. Richards-Babb July 9, 1998 An optical scoring machine will grade this examination. The machine is not programmed to accept the correct one of two sensed answers and will not sense answers which are lightly marked. Mark your answer sheet carefully with a No. 2 soft lead pencil and erase any undesired marks COMPLETELY. Avoid making any extraneous marks on the answer sheet other than the information requested below. On the answer sheet: 1. Print your name in the space for NAME (last name first, circle your last name). 9 2. In the space marked SUBJECT print your student number. 3. In the'space marked HOUR print Summer 11 ‘98. Check to see that you have 20 examination questions and a periodic table when the exam begins. HAND TN ONLY THE ANSWER SHEET. Useful Equations and Constants: - KAH20)=1.86 kg-°C/mol Kb(H20)=0.52 kg-°C/mol 1atm=760 torr=760 mm Hg R=0.08206 L-atm/mol-‘K=8.3 l4 J/mol-K CHEMISTRY 16 HOUR EXAM I CHOOSE THE ONE BEST ANSWER. 1. What volume (in mL) of a solution that is 0.750 M Al(NO3)3 will provide 0.0500 mol of nitrate ions? A. 22.2 mL B. 200. mL C. 112 mL D. 70.7 mL E. 15.0 mL 2. Write the net ionic equation for the following reaction that occurs in aqueous solution. Ions that do not appear in the net ionic equatiOn (ie. spectator ions) are: H.130. + Mg(NOs)2 —» Mme.» + PM. A. Mg+2 and P04‘3 B. H+ and ND; C. NO; only D. Mg+2 and H+ E. All ions are spectator ions. 3. Which of the following compounds acts as a weak electrolyte when dissolved in water? A. CaC12 B. NaOH C. H2804 D. HC2H302 E. All of the above. 4. A solution is 0.1 M in Pb+2 and Sr”. Addition of 'HBr(aq) will precipitate while addition of K2$O4(aq) will precipitate (HINT: Predict products and solubility) A PbBrz and SrBrZ; PbSO4 B. PbBr2 and SrBrZ; PbSO4 and SrSO4 C. PbBrz; PbSO4 D. PbBrz; PbSO4 and SrSO4 E. Nothing; Nothing Which of the following mixtures have components which can be separated by filtration? A. Milk B. Blood C. Seawater D. Lemonade E. Wine - ' Which should be least soluble in water? A. C4Hlo (butane) H- -O-H (formic acid) CH3OH (methanol) HzN-CH3 (methylamine) KBr P1909” A temperature increase causes the solubility of gaseous O2 in freshwater to ; while a temperature increase causes the solubility of solid NH4NO3 in water to . (The dissolution of NH4NO3 in water is endothermic) increase; decrease decrease; increase decrease; decrease increase; increase decrease; temperature has no effect on the solubility of an ionic compound in water. mpow> The Henry’s Law constant of gaseous methyl bromide CH3Br is k=0. 159 mol/L-atm at 25°C. What mass of gaseous CH3Br will dissolve in 225 mL of water at 25°C and at a CH3Br partial pressure of 250. mm Hg? (Molar Mass CH3Br = 94.93) A. 5.23 g B. 3.40 g C. 8.49 g D. 22.1 g E. 1.12 g A 1.30 M solution of CaCl2 in water has a density of 1.11 g/mL. The molality of CaCl2 is: (Molar Mass CaC12=l 10.99) A. 1.17 m B. 1.44 m C. 1.30 m D. 0.854 m E. 1.35 m 10. 11. 12. 13. 14. ' A solution of liquid toluene dissolved in liquid benzene has a benzene mole fraction of 0.850. Calculate the vapor pressure of the solution given that the vapor pressures of pure benzene and toluene are 183 mm Hg and 59.2 mm Hg, respectively. A. 155 mm Hg B. 206 mm Hg C. 164 mm Hg D. 124 mm Hg E. 50.3 mm Hg A solution is prepared by' dissolving 0.131 mol of sugar, C‘anO”, in 175 g of water. The amount by which the vapor pressure is lowered is: (The vapor pressure of water is 23.76 mm Hg at 25°C) A 23.00mm Hg g B. 0.316mmHg C. 17.8 mm Hg D 3.11 mm Hg E 1.33 mm Hg Which one of the aqueous solutions below will have the highest boiling point? A. 0.012 m KCl B. 0.0080 rn BaClz C. 0.0080 m K2SO4 D. 0.0060 m Al(NO3)3 E. All have about the same boiling point. A solution is made by dissolving 20.0 g C7H602 in 800 g C6H6. The freezing point of the resulting solution is: .(K.(C6H6)=5.10 kg-°C/mol; T,(C6H6)=5.50°C) A. 4.46 °C 'B 3.75 °c c. 5.50 °C D. 4.22 °c E» 6.54 °‘c A 100.40 °C B. 101.71 °C C. 100.22 °C D 100.89 °C E ‘ 99.11 °C 15. 16. 17. A 0.15 g sample of a protein is dissolved in enough water to give 2.0 mL of solution. The osmotic pressure of the resulting solution is 18.6 mm Hg at 25°C. The molar mass of the protein is: A. 2.0><106 g/mol B. l.3><105 g/mol C. 99 g/mol D. 7.5><104 g/mol E. 6.3><103 g/mol Red blood cells are filled with an aqueous solution of various solutes and the cell walls act as a semipermeable membrane. A red blood cell is taken from the bloodstream and placed into pure water. Which of the following statements is TRUE? Water molecules flow out of the red blood cells, causing them to collapse. The osmotic pressure exerted on the cell walls remains constant. Water flows into the red blood cells, causing them to swell and burst. Solute flows out of the red blood cells causing a decrease in osmotic pressure. The osmotic pressure of the pure water is greater than the pressure inside the red blood cells, causing them to constrict. wcow> Given the initial rate data shown below, calculate the rate law for the following reaction. 2 HgC12(aCI) + C204'2(aQ) —' 2 C1—(aCI) + 2 C02(g) + Hg2C12(S) LHngzl [£2Q421 Initial Rate 1M/sec) 0.10 0.20 5.20><10‘7 0.10 . 0.40 ' 2.08X10‘6 0.30 0.20 1.56X10'6 Rate = k [HgC12]2[C204‘2]2 Rate = k [HgC12]2[C204’2] Rate = k [HgClz][C204’2]2 Rate = k [ch12]3[czo.-2]4 Rate = k [ch12][czo.-2] PLUGS”? 18. 19. 20. £113.09“? The reaction shown below has the rate law Rate = k[A][B]2. Which of the following will NOT increase the rate of the reaction? 3 A '+ B + C —+ Products Increase. in concentration of reactant C. A temperature change from 100°C to 25°C. Doubling of [B] but a halving of [A]. Answers A, B, and C will NOT increase the rate. Answers A and B will NOT increase the rate. The reaction below occurs in the Breathalyzer when determining alcohol level in the bloodstream. 2 KzCr207 + 8 H2804 + 3 CZHGO -* 2 Cr2(SO4)3 + 2 K2504 + 3 C2H402 +11 H20 Calculate the rate of disappearance of C2H6'O if the rate of appearance of Cr2(SO4)3 is 2.48 M/min. A. 7.44 M/min B. 3.72 M/min C. 4.96 M/min D. 1.65 M/min E. 0.827 M/min A reaction has the following rate law: Rate = k[C4H9Br][OH‘]°. If the rate of the reaction is 2.2X10“ M/sec when [C4H9Br]=0.50 M and [OH‘]=0.25 M, what is the value of the rate constant, k? A. 4.4><10"4 sec'l B. 1.1><10“‘ sec" C. 1.8><10‘3 sec" D. ' 2.8><10" sec" E. None of the above. ...
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