Chemistry 116: Exam 1A (Ratcliff) February 3, 2015

Transcription

1 1. Which is correctly arranged by increasing chloride concentration? Lowest [Cl ] Highest [Cl ] a. 1M CaCl2 < 1M FeCl3 < 2M CaCl2 < 5M NaCl < 2M FeCl3 b. 2M CaCl2 < 2M FeCl3 < 1M CaCl2 < 1M FeCl3 < 5M NaCl c. 2M CaCl2 < 2M FeCl3 < 1M CaCl2 < 1M FeCl3 < 5M NaCl d. 2M FeCl3 < 5M NaCl < 2M CaCl2 < 1M FeCl3 < 1M CaCl2 e. 5M NaCl < 1M CaCl2 < 1M FeCl3 < 2M CaCl2 < 2M FeCl3 2. Calculate the molality of a solution that is 1.27 M sugar, g/mole. The density of the solution is 1.12 g/ml. a mole/ kg b mole/ kg c mole/ kg d mole/ kg e mole/ kg 3. A 283 ml benzene solution containing 2.97 g of an organic polymer has an osmotic pressure of 7.39 mm Hg at 23 o C. Calculate the molar mass of the polymer. a g/mole b g/mole c g/mole d g/mole e g/mole 4. Which of the following are the requirements of an effective collision between two or more molecules? I. correct orientation II. sufficient kinetic energy III. presence of a catalyst IV. high temperature a. I only b. II only c. I and II only d. I, II, and III e. I, II, III, and IV 5. The atomic view of four 0.5M solutions is shown below. Assuming that the solutions behave ideally, which solution has the highest osmotic pressure? a. b. c. d. It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 1 of 5

2 6. Calculate the concentration of oxygen at 25 o C at a partial pressure of 0.22 atm. The Henry s Law constant for oxygen at 25 o C is mol/l atm. a mole/ L b mole/ L c mole/ L d mole/ L e mole/ L 7. Calculate the molality of a solution that is 43.7 percent NaCl by mass a. Cannot determine, need to know the density of solution. b mole/ kg c mole/ kg d mole/ kg e mole/ kg 8. What is the mole fraction of Ar in a gaseous mixture containing 10.1 grams of Ne, 79.9 grams of Ar, and 84 grams of Kr? a b c d e Children under the age of six with more than 0.10 ppm of lead in their blood can suffer a reduction in I.Q. or have behavior problems. What is the molality of a solution which contains 0.10 ppm of lead? Assume the density of solution is the same as water. a m b m c m d m e m 10. Calculate the vapor pressure of a solution made by dissolving 87.6 grams of urea (molar mass = g/mol) in grams of water at 35 o C. (Hint: The vapor pressure of water at 35 o C is mmhg.. a mmhg b mmhg c mmhg d mmhg e mmhg It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 2 of 5

3 11. The initial drawing shows the equilibrium vapor pressure of a pure liquid. Which drawing represents the equilibrium vapor pressure when a nonvolatile solute is dissolved in the liquid? 12. Normal tap water contains a small amount of dissolved oxygen. What (if anything) happens to the solubility of oxygen in water as the water is heated? a. There is no way to predict b. The solubility of oxygen in water decreases c. The solubility of oxygen in water increases d. The solubility of oxygen in water stays the same 13. A saturated solution of carbon dioxide in water contains 3.00 g of CO2 when the CO2 partial pressure is 8.0 atm. What mass of CO2 will escape if the partial pressure is lowered to 3.2 atm? a g b g c g d g e g 14. The atomic view of four 0.5M solutions is shown below. Assuming that the solutions behave ideally, which solution has the highest freezing point? a. b. c. d. 15. Calculate the van't Hoff factor, i, of Na3PO4 in a 0.40 m solution whose freezing point is 2.6 o C. Kf for water is 1.86 C/m a. 3.2 b. 2.8 c. 3.5 d. 3.9 e. 2.4 It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 3 of 5

4 16. The vapor pressures of ethanol (C2H5OH) and 1 propanol (C3H7OH) at 35 o C are 100 mmhg and 37.6 mmhg respectively. Calculate the partial pressures of ethanol and 1 propanol above a solution of ethanol and 1 propanol, in which the mole fraction of ethanol is Assume ideal behavior and the temperature is 35 o C. Ethanol 1 propanol a mmhg 27.1 mmhg b mmhg 7.56 mmhg c mmhg 10.5 mmhg d mmhg 27.1 mmhg e mmhg 27.9 mmhg 17. Use your knowledge of collision theory and the potential energy diagram shown to estimate the activation energy of the forward reaction a. +25 kj b. +45 kj c. +15 kj d. +10 kj e. +35 kj 18. How does the concentration of dissolved oxygen and nitrogen in the bloodstream change as a scuba diver swims to lower depths of the ocean? a. There is no way to predict b. The diver experiences decreasing pressures with increasing depth and, hence acquires increasing concentration of gases in his bloodstream. c. The diver experiences increasing pressures with increasing depth and, hence acquires increasing concentration of gases in his bloodstream. d. The diver experiences decreasing pressures with increasing depth and, hence acquires decreasing concentration of gases in his bloodstream. e. The diver experiences increasing pressures with increasing depth and, hence acquires decreasing concentration of gases in his bloodstream. 19. What mass of KI is dissolved in grams of a solution that is 45.0 % KI by mass? a grams b grams c. 385 grams d. 315 grams e. 156 grams It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 4 of 5

5 20. A solution of g of an organic compound in g of benzene has a freezing point of o C. What is the molality of the solution? The normal freezing point for benzene is o C and Kf for benzene is 5.12 o C/m a mole/ kg b mole/ kg c mole/ kg d mole/ kg e. Cannot determine without more information Bonus Question 21. Consider the three mercury manometers shown in the diagram. One of them has 1 ml of water on top of the mercury, another has 1 ml of a 1m urea (a non-electrolyte) solution on top of the mercury and the third one has 1 ml of a 1m NaCl solution placed on top of the mercury. Which of these of these solutions is in the tube labeled X, which is in Y, and which is in Z? 1 ml water 1 ml 1m urea 1 ml of 1m NaCl a. Z X Y b. X Z Y c. X Y Z d. Y Z X e. Y X Z Key 1. A 2. D 3. C 4. C 5. A 6. E 7. D 8. E 9. B 10. A 11. B 12. B 13. D 14. D 15. C 16. A 17. A 18. C 19. D 20. D 21. B It s not that I m so smart, it s just that I stay with problems longer. ~ Albert Einstein Page 5 of 5