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Chemistry 112, Spring 2008 , Section 1& 3 (Hardy) Exam 1 (100 points) 18 Feb 2009 YOU MUST: Put your name and student ID on the bubble sheet correctly. Put the exam version ID on the bubble sheet. The exam number is found on the subsequent pages e.g. ID:A, ID:B, ID:C etc. Put all your answers on the bubble sheet.
- This exam has 20 required questions and 2 extra credit questions. The questions have been randomly sorted so your extra credit questions may be in the middle of the exam.
- There is no penalty for guessing so you should answer all the questions.
- Please keep your eyes on your own paper and your answers covered.
- Use the exam as scratch paper. I will not grade anything on the exam itself.
- You may take the exam with you when you finish, so you only need to put your name on the bubble sheet.
- Turn the bubble sheet in to the appropriate stack when you are done. Good luck!
Name: ______________________ Class: _________________ Date: _________ ID: D
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Multiple Choice Identify the choice that best completes the statement or answers the question. ____ 1. What mass of Na 2 SO 4 must be dissolved in 75.0 grams of water to lower the freezing point by 2.50 °C? The freezing point depression constant, K fp, of water is –1.86 °C/ m. Assume the van't Hoff factor for Na 2 SO 4 is 2.40. a. 23.3 g b. 44.0 g c. 0.310 g d. 5.97 g e. 3.30 g ____ 2. Which of the following phase transitions is/are exothermic?
- liquid water evaporating into the gas phase.
- the sublimation of solid carbon dioxide into the gas phase.
- gaseous butane condensing into a liquid at its boiling point of –0.5 °C. a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3 ____ 3. Normal boiling point is defined as a. the pressure of a gas when its temperature reaches 273.15 K. b. the temperature at which the enthalpy of vaporization equals 100.0 kJ/mol. c. the temperature at which the vapor pressure of a liquid equals 1 atm. d. the pressure at which any liquid boils at 373.15 K. e. the temperature at which water always boils. ____ 4. Which action(s) will increase the equilibrium concentration of a non-reacting gas in water?
- decreasing the temperature of the water
- increasing the volume of water
- decreasing the pressure of the gas above the liquid a. 1 only b. 2 only c. 3 only d. 1 and 3 e. 1, 2, and 3
Name: ______________________ ID: D ____ 10. The heat of formation of NaCl(s) is –411.1 kJ/mol and the heat of formation of NaCl(aq, 1 m ) is –407. kJ/mol. Determine the heat of solution of NaCl. Will the solution temperature increase or decrease when NaCl is dissolved in water? a. –818.4 kJ/mol; decrease b. –3.8 kJ/mol; increase c. +3.8 kJ/mol; decrease d. +818.4 kJ/mol; increase e. +3.8 kJ/mol; increase ____ 11. Which one of the following molecules will exhibit dipole-dipole intermolecular forces as a pure liquid? a. CO 2 b. C 2 H 2 c. SO 3 d. NO 2 e. F 2 ____ 12. If 355 g of ethanol (C 2 H 5 OH) is added to 645 g of water, what is the molality of the ethanol? a. 55.0 m b. 7.71 m c. 21.7 m d. 11.9 m e. 0.550 m ____ 13. If 18.4 g KCl is dissolved in 2.50 × 102 g H 2 O, what is the weight percent of KCl in the solution? a. 97.2% b. 7.36% c. 6.86% d. 7.94% e. 0.972% ____ 14. Which of the following are valid reasons why vegetable oil has a greater viscosity than diethyl ether, CH 3 OCH 3?
- Unlike diethyl ether, oil molecules are not held together by hydrogen bonds.
- Oil molecules have long chains that become entangled.
- Intermolecular forces are greater for the larger oil molecules. a. 1 only b. 2 only c. 3 only d. 1 and 3 e. 2 and 3 ____ 15. EXTRA CREDIT. After the CaCO3 shell of an egg is dissolved in acetic acid, the egg membrane is left holding the egg intact. What function can this membrane play? a. It mantains the vapor pressure of the egg white when the egg is bathed in water. b. It is a semi-permiable colloide. c. It maintains the low boiling point of the egg yolk. d. It can act as an osmotic membrane. e. It can act as a kidney dialysis device.
Name: ______________________ ID: D ____ 16. The osmotic pressure of blood is 7.65 atm at 37 °C. What mass of glucose (C 6 H1 2O 6 , molar mass = 180. g/mol) is needed to prepare 2.25 L of solution for intravenous injection? The osmotic pressure of the glucose solution must equal the osmotic pressure of blood. ( R = 0.08206 L⋅atm/mol⋅K) a. 1.02 × 103 g b. 5.67 g c. 122 g d. 0.698 g e. 0.676 g ____ 17. At its boiling point of –34.0 °C, 6.33 kJ of heat is required to vaporize 22.0 g of chlorine (Cl 2 ). What is the molar enthalpy of vaporization of chlorine? a. 0.286 kJ/mol b. 20.4 kJ/mol c. 0.0893 kJ/mol d. 139 kJ/mol e. 1.96 kJ/mol ____ 18. The Henry's law constant for N 2 in water at 37 °C is 8.2 × 10 – 7^ M/mm Hg. What is the equilibrium concentration of N 2 in water when the partial pressure of N 2 is 605 mm Hg? a. 2.0 × 103 M b. 5.0 × 10 – 4^ M c. 6.5 × 10 – 7^ M d. 7.4 × 108 M e. 1.4 × 10 – 9^ M ____ 19. If 3.01 g of water is sealed in an evacuated 2.00 L flask and heated to the normal boiling point of 373 K, what is the pressure in the flask? ( R = 0.08206 L⋅atm/mol⋅K) a. 2.56 atm b. 1.00 atm c. 0.678 atm d. 0.391 atm e. 46.1 atm ____ 20. Mount Everest rises to a height of 8.850 × 103 m above sea level. At this height, the atmospheric pressure is 231 mm Hg. At what temperature (in °C) does water boil at the summit of Mount Everest? The vapor pressure of water at 373 K is 760.0 mm Hg. (Δvap H ° for H 2 O = 40.7 kJ/mole and R = 8. J/K⋅mol) a. 72 °C b. 69.0 °C c. 4.07 °C d. 87 °C e. 364 °C
ID: D
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Answer Section
MULTIPLE CHOICE
- ANS: D PTS: 1 TOP: 14.4 Colligative Properties
- ANS: C PTS: 1 TOP: 12.4 Properties of Liquids
- ANS: C PTS: 1 TOP: 12.4 Properties of Liquids
- ANS: A PTS: 1 TOP: 14.3 Factors Affecting Solubility: Pressure and Temperature
- ANS: A PTS: 1 TOP: 12.4 Properties of Liquids
- ANS: D PTS: 1 TOP: 12.3 Interactions Involving Nonpolar Molecules
- ANS: B PTS: 1 TOP: 14.4 Colligative Properties
- ANS: B PTS: 1 TOP: 14.1 Units of Concentration
- ANS: C PTS: 1
- ANS: C PTS: 1 TOP: 14.2 The Solution Process
- ANS: D PTS: 1 TOP: 12.2 Intermolecular Forces Involving Polar Molecules
- ANS: D PTS: 1 TOP: 14.1 Units of Concentration
- ANS: C PTS: 1 TOP: 14.1 Units of Concentration
- ANS: E PTS: 1 TOP: 12.4 Properties of Liquids
- ANS: D PTS: 1
- ANS: C PTS: 1 TOP: 14.4 Colligative Properties
- ANS: B PTS: 1 TOP: 12.4 Properties of Liquids
- ANS: B PTS: 1 TOP: 14.3 Factors Affecting Solubility: Pressure and Temperature
- ANS: B PTS: 1 TOP: 12.4 Properties of Liquids
- ANS: B PTS: 1 TOP: 12.4 Properties of Liquids
- ANS: E PTS: 1 TOP: 14.4 Colligative Properties
- ANS: D PTS: 1 TOP: 13.6 Phase diagrams
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