Chem 1046 February 27, 2001 Test #2 1. A sample of octane in equilibrium with its vapor in a closed 1.0-L container has a vapor pressure of 50.0 torr at 45 C. The container s volume is decreased to 0.50 L at constant temperature and the liquid/vapor equilibrium is reestablished. What is the vapor pressure? a. > 50.0 torr b. 50.0 torr c. < 50.0 torr d. the mass of the octane vapor is needed to calculate the vapor pressure 2. Liquid ammonia (boiling point = -33.4 C) can be used as a refrigerant and heat transfer fluid. How much energy is needed to heat 25.0 g of NH 3 (l) from -65.0 C to -12.0 C? Specific heat capacity, NH 3 (l) Specific heat capacity, NH 3 (g) Heat of vaporization Molar mass, M 4.7 J/(g K) 2.2 J/(g K) 23.5 kj/mol 17.0 g/mol a. 5.5 kj b. 39 kj c. 340 kj d. 590 kj 1
3. Examine the following phase diagram and identify the feature represented by point A. a. melting point b. critical point c. triple point d. sublimation point 4. Examine the following phase diagram and identify the feature represented by point B. a. melting point b. triple point c. critical point d. sublimation point 2
5. Consider the following phase diagram and identify the process occurring as one goes from point C to point D. a. increasing temperature with a phase change from solid to liquid b. increasing temperature with a phase change from solid to vapor c. increasing temperature with a phase change from liquid to vapor d. increasing temperature with no phase change 6. The condensation of neon is due to a. dipole-dipole forces b. covalent bonding c. hydrogen bonding d. London dispersion forces 7. Ammonia s unusually high melting point is the result of a. dipole-dipole forces b. London dispersion forces c. hydrogen bonding d. covalent bonding 8. The strongest intermolecular interactions between pentane (C 5 H 12 ) molecules arise from a. dipole-dipole forces b. London dispersion forces c. hydrogen bonding d. ion-dipole interactions 9. Which of the following will form hydrogen bonds in the pure state? a. (CH 3 ) 3 N b. CH 3 O CH 3 c. CH 3 CH 2 OH d. CH 3 CH 2 F 3
10. Which of the following will not form hydrogen bonds in the pure state? a. b. c. d. 11. Which of the following should have the highest boiling point? a. CF 4 b. CCl 4 c. CBr 4 d. CI 4 12. Select the pair of compounds in which the substance with the higher vapor pressure at a given temperature is listed first. a. C 7 H 16, C 5 H 12 b. CCl 4, CBr 4 c. H 2 O, H 2 S d. CH 3 CH 2 OH, CH 3 O CH 3 13. The resistance of a liquid to flow is a. surface tension b. capillary action c. viscosity d. adhesion 14. Which one of the following substances does not exist in the indicated solid type? a. graphite - network b. Na - metallic c. SiO 2 - molecular d. NaCl - ionic e. diamond - network 4
15. When liquid bromine is cooled to form a solid, which of the following types of solid would it form? a. atomic b. metallic c. molecular d. ionic e. covalent network 16. A solution of sucrose (sugar) in water is in equilibrium with solid sucrose. If more solid sucrose is now added, with stirring, a. the concentration of the solution will increase. b. the concentration of the solution will decrease. c. the concentration of the solution will remain the same. d. a supersaturated solution will be produced. 17. A solution of potassium hydroxide is in equilibrium with undissolved solute at 45 C. What will happen if the temperature is raised to 50 C? ( H soln = -57.6 kj/mol) a. The mass of dissolved KOH will increase. b. The mass of dissolved KOH will decrease. c. The mass of dissolved KOH will be unchanged. d. The mass of water in the solution will increase. 18. What is the molality of a solution prepared by dissolving 86.9 g of diethyl ether, C 4 H 10 O, in 425 g of benzene, C 6 H 6? a. 0.362 m b. 0.498 m c. 2.01 m d. 2.76 m 19. Procaine hydrochloride (M = 272.77 g/mol) is used as a local anesthetic. Calculate the molarity of a 4.666 m solution which has a density of 1.1066 g/ml. a. 2.272 M b. 4.056 M c. 4.216 M d. 4.666 M 5
20. Colligative properties depend on a. the chemical properties of the solute. b. the chemical properties of the solvent. c. the number of particles dissolved. d. the molar mass of the solute. 21. Select the aqueous solution which should have the highest boiling point. a. 1.0 M KNO 3 b. 0.75 M NaCl c. 0.75 M CuCl 2 d. 2.0 M C 12 H 22 O 11 (sucrose) 22. How many moles of lithium ions are present in 1.0 L of 0.5 M Li 2 SO 4? a. 0.5 mol b. 1.0 mol c. 1.5 mol d. 3.0 mol 23. Which of the following aqueous solutions will have the lowest freezing point? a. 0.5 m C 12 H 22 O 11 (sucrose) b. 0.5 m Ca(NO 3 ) 2 c. 0.5 m NiSO 4 d. 0.5 m Li 3 PO 4 24. Benzaldehyde (M = 106.1 g/mol), also known as oil of almonds, is used in the manufacture of dyes and perfumes and in flavorings. What would be the freezing point of a solution prepared by dissolving 75.00 g of benzaldehyde in 850.0 g of ethanol? K f = 1.99 C/m, freezing point of pure ethanol = -117.3 C a. -117.5 C b. -118.7 C c. -119.0 C d. -120.6 C 6
25. Dimethylglyoxime, DMG, is an organic compound used to test for aqueous nickel(ii) ions. A solution prepared by dissolving 65.0 g of DMG in 375 g of ethanol boils at 80.3 C. What is the molar mass of DMG? K b = 1.22 C/m, boiling point of pure ethanol = 78.5 C a. 44.1 g/mol b. 65.8 g/mol c. 117 g/mol d. 553 g/mol 26. A 0.100 m K 2 SO 4 solution has a freezing point of -0.43 C. What is the van t Hoff factor for this solution? K f = 1.86 C/m a. 0.77 b. 1.0 c. 2.3 d. 3.0 27. Human blood has a mo lar concentration of solutes of 0.30 M. What is the osmotic pressure of blood at 25 C? (R = 0.0821 L atm/mole K) a. 0.012 atm b. 0.62 atm c. 6.8 atm d. 7.3 atm 28. Lysine is an amino acid that is an essential part of nutrition but which is not synthesized by the human body. What is the molar mass of lysine if 750.0 ml of a solution containing 8.60 g of lysine has an osmotic pressure of 1.918 atm? T = 25.0 C a. 110 g/mol b. 146 g/mol c. 1340 g/mol d. 1780 g/mol 7
29. In which of the following would the boiling point of water be highest? A) at the peak of Mt. Everest B) in a pressure cooker where the pressure is 1400 Torr C) in the "mile high" city of Denver D) in New York city where the pressure is about 760 Torr E) in New Mexico where the pressure is about 710 Torr 30. The triple point of carbon dioxide is 56 C and 5.1 atm. The critical temperature is 31 C. Liquid carbon dioxide can exist at A) 1 atm and 56 C. B) 10 atm and 70 C. C) 10 atm and 25 C. D) 10 atm and 33 C. E) 5.1 atm and 25 C. 31. The critical temperature of HCl is 52 C. At temperatures above 52 C, A) HCl can be liquefied if the pressure applied is greater than the critical pressure. B) HCl cannot be liquefied no matter what the pressure. C) HCl decomposes into the atoms H and Cl. D) HCl exists exclusively as a liquid. E) HCl decomposes into its constituent elements. 32. Which of the following would likely dissolve in water? A) C 6 H 6, benzene B) CaCl 2 C) CCl 4 D) C 6 H 5 Cl 33. Which of the following would most likely dissolve in CCl 4? A) CaCO 3 B) H 2 O C) NH 4 NO 3 D) I 2 8