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Material Type: Exam; Professor: Voigtman; Class: Gen Chem-Sci; Subject: Chemistry; University: University of Massachusetts - Amherst; Term: Unknown 1989;
Typology: Exams
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Multiple Choice Identify the choice that best completes the statement or answers the question. ____ 1. Which of the following statements concerning the attraction of ions to polar molecules is/are CORRECT?
c. dipole-dipole force and induced dipole/induced dipole force d. hydrogen bonding and induced dipole/induced dipole force e. hydrogen bonding, dipole-dipole force, and induced dipole/induced dipole force ____ 5. Equilibrium is established between a liquid and its vapor when a. the rate of evaporation equals the rate of condensation. b. equal masses exist in the liquid and gas phases. c. equal concentrations (in molarity) exist in the liquid and gas phases. d. all the liquid has evaporated. e. the liquid ceases to evaporate and the gas ceases to condense. ____ 6. Which of the following liquids has the smallest enthalpy of vaporization? a. C 5 H 12 b. C 4 H 10 c. C 3 H 8 d. C 2 H 6 e. C 6 H 14 ____ 7. At 65.0 °C, water has an equilibrium vapor pressure of 187.5 mm Hg. If 4.78 g H 2 O is sealed in an evacuated 5.00 L flask and heated to 65.0 °C, what mass of H 2 O will be found in the gas phase when liquid-vapor equilibrium is established? Assume any liquid remaining in the flask has a negligible volume. ( R = 0. L⋅atm/mol⋅K, 1 atm = 760 mm Hg) a. 0.0444 g b. 0.801 g c. 1.87 g d. 4.167 g e. 4.78 g ____ 8. Sulfur dioxide has a vapor pressure of 462.7 mm Hg at – 21.0 °C and a vapor pressure of 140.5 mm Hg at – 44.0 °C. What is the enthalpy of vaporization of sulfur dioxide? ( R = 8.314 J/K⋅mol) a. 0.398 kJ/mol b. 6.33 kJ/mol c. 14.0 kJ/mol d. 24.9 kJ/mol e. 39.8 kJ/mol ____ 9. Which of the following phase transitions is/are exothermic?
b. +3.8 kJ/mol; increase c. +3.8 kJ/mol; decrease d. +818.4 kJ/mol; increase e. – 818.4 kJ/mol; decrease ____ 14. Which action(s) will increase the equilibrium concentration of a non-reacting gas in water?
____ 18. What is the boiling point of a solution containing 0.80 g caffeine, C 8 H 10 N 4 O 2 , dissolved in 13.20 g benzene? The boiling point of pure benzene is 80.1 °C and the boiling point elevation constant, K bp, is 2.53 °C/ m. a. (^) 79.8 °C b. (^) 80.4 °C c. (^) 80.9 °C d. (^) 85.2 °C e. (^) 88.2 °C ____ 19. What concentration unit is used in the calculation of osmotic pressure for a dilute solution? a. molality b. weight percent c. mass fraction d. mole fraction e. molarity ____ 20. A solution is prepared by dissolving 4.78 g of an unknown nonelectrolyte in enough water to make 375 mL of solution. The osmotic pressure of the solution is 1.33 atm at 27 °C. What is the molar mass of the solute? ( R = 0.08206 L⋅atm/mol⋅K) a. 0.0203 g/mol b. 21.2 g/mol c. 49.4 g/mol d. 96.8 g/mol e. 236 g/mol