1 CHEM 1032 PRACTICE EXAM I CLASS SPRING 2017 1. Select the characteristic(s) of the liquid phase: (You may need a periodic table. Useful information appears on page 5.) (i) adopts the shape of the container (iii) particles exhibit no translational motion (ii) highest energy of the 3 main states of mater (iv) lower density than the gas phase A. (i) B. (i) and (iv) C. (ii) and (iii) D. all 4 2. What are all the intermolecular forces present in liquid SO 3? (EN: S = 2.5, O = 3.5). A. ion-dipole C. dipole-dipole B. dispersion D. dispersion and dipole-dipole Given the 3 compounds: X = CCl 4, Y = CH 3 OH, and Z = Ba(NO 3 ) 2, use them to answer questions 3 6. 3. Which compound would you expect be the least volatile? A. X B. Y C. Z D. insufficient info. 4. Which compound(s) would you expect be soluble in water? A. X and Y B. Y C. Y and Z D. X, Y and Z 5. Which compound(s) would you expect be soluble in 1-heptanol, CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 OH? A. X B. X and Y C. Y D. Z 6. The explanation for the answer to question 5 is: A. the solute and solvent are both polar C. the solute and solvent are both non-polar B. the solute is polar and the solvent is non-polar D. the solute is non-polar and the solvent is polar 7. The vapor pressure of a liquid depends on the: (i) external pressure (iii) strength of the intermolecular forces (ii) temperature (iv) surface of area of the liquid in the container A. all 4 B. (i), (ii) and (iii) C. (ii), (iii) and (iv) D. (ii) and (iii) 8. Which of the following liquids is the most viscous? A. CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 C. CH 3 CH 2 CH 2 -O-CH 2 CH 2 CH 3 B. CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 OH D. CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 Br
2 The vapor pressure, in mmhg, of a liquid was measured at various temperatures and the results are graphed below. Use the information in the plot to answer questions 9 13. 3.4 3.3 3.2 3.1 3 2.9 y = -5310x + 20.977 2.8 2.7 2.6 2.5 0.0033 0.00335 0.0034 0.00345 0.0035 9. What is plotted on the axes? A. x = lnp vap ; y = 1/T (K 1 ) C. x = 1/T (K 1 ); y = lnp vap B. x = T (K); y = P vap D. x = lnt; y = 1/P vap (mmhg 1 ) 10. What is the enthalpy of condensation, H cond, for the liquid? A. 5.31 kj/mol B. 44.1 kj/mol C. 5.31 kj/mol D. 44.1 kj/mol 11. What is the normal boiling point of the liquid? A. 253 K B. 370. o C C. 370. K D. 801 K 12. What property of the liquid must remain constant in order to produce the straight line shown in the graph? A. vapor pressure B. H vap C. temperature D. rate of vaporization 13. What is the vapor pressure of the liquid at a temperature of 30.0 o C? A. 3.45 atm B. 2.46 x 10 8 mmhg C. 156 mmhg D. 4.15 x 10 2 atm 14. The van t Hoff factor is most often used for solutes. A. molecular B. volatile C. non-volatile D. ionic 15. The experimentally observed value of the van t Hoff factor is generally the expected value. A. less than B. equal to C. greater than D. any of these
3 The primary components of the antifreeze solution in vehicle radiators are a 50.0 % by volume solution of ethylene glycol (HOCH 2 CH 2 OH; MM = 62.07 g/mol; density = 1.11 g/ml) and water. The density of the solution is 1.07 g/ml. Use this information to answer questions 16 21. 16. Ethylene glycol and water are miscible. This observation indicates that the dominant intermolecular force in ethylene glycol is: A. dispersion B. dipole-dipole C. hydrogen bonding D. ion-dipole 17. Calculate the mass percent of the ethylene glycol in the solution. A. 52.6 % B. 55.5 % C. 50.0 % D. 51.9 % 18. Calculate the molality of the ethylene glycol in the solution. A. 0.753 m B. 0.836 m C. 17.4 m D. 8.94 m 19. Calculate the molarity of the ethylene glycol solution. A. 0.753 M B. 0.836 M C. 17.4 M D. 8.94 M 20. Calculate the expected freezing point of the solution. K f for water = 1.86 o C/m. A. 32.4 o C B. 16.6 o C C. 16.6 o C D. 32.4 o C 21. Calculate the vapor pressure of the water above the solution (assume ethylene glycol is non-volatile) at 25 o C. The vapor pressure of water at 25 o C is 23.8 mmhg. A. 5.66 mmhg B. 11.9 mmhg C. 25.0 mmhg D. 18.1 mmhg 22. Choose the condition below that would result in an enthalpy of solution close to zero. A. When H lattice < H hydration C. When H lattice > H hydration B. When H solvent > H solute D. When H lattice H hydration 23. Which of the following compounds would you expect to be the least soluble in water? A. LiNO 3 B. Al 2 O 3 C. MgO D. KF 24. If you monitor the temperature during the dissolution of sodium hydroxide in water, which of the following observations would you make? (NaOH: H lattice = 877 kj/mol; H hydration = 932 kj/mol). A. the temperature of the solution would increase C. the temperature of the solution would decrease B. there would be no change in temperature D. unable to predict a change in temperature
Cyclohexane freezes at 6.50 C and has a K f value of 20.0 C/m. A mixture of caffeine (a non-electrolyte) and cyclohexane (C 6 H 12 ) was prepared by adding 3.00 g of caffeine to 25.00 g of cyclohexane. The mixture produced a homogeneous solution. The freezing point of the solution was found to be equal to 5.90 o C. Use this information to answer questions 25 27. 25. What is the freezing point depression? 4 A. 0.60 o C B. 12.40 o C C. 5.90 o C D. 12.40 o C 26. What is the molality of the solution? A. 11.9 m B. 1.61 m C. 0.620 m D. 0.120 m 27. What is the molar mass of caffeine? A. 194 g/mol B. 1,610 g/mol C. 84.2 g/mol D. 4,000 g/mol The Henry s Law constant at 25 o C for carbon dioxide (MM = 44.01 g/mol) in water is 0.034 M/atm. A bottle of soda contains 355 ml of liquid (assume mainly water) and 2.2 g of dissolved CO 2. Use this information to answer question 28 30. 28. Calculate the pressure of CO 2 required to dissolve all of it at 25 o C. A. 4.1 atm B. 1.9 atm C. 1.5 atm D. 0.24 atm 29. If the soda is prepared at a temperature below 25 o C, the pressure of CO 2 required to dissolve the same mass of CO 2 in 355 ml would be the pressure that was required at 25 o C. A. greater than B. less than C. equal to D. insufficient info. 30. Immediately after a bottle of soda is opened, the concentration of CO 2 in the solution: A. increases B. decreases C. stays the same D. insufficient info. 31. A non-volatile liquid has a vapor pressure of 456 mmhg at a temperature of 135 o C and a vapor pressure of 256 mmhg at a temperature of 120 o C. What is the normal boiling point of the liquid? A. 149 o C B. 225 o C C. 356 o C D. 407 o C
5 Useful information: 1 atm = 760 mmhg 1 mmhg = 1 torr 0 ºC = 273 K R = 8.314 J/(mol.K) P H 2 vap 1 1 H vap 1 ln - lnp vap = P1 R T2 T1 R T + ln volume of solute volume percent = volume of solution H solution = H lattice + H hydration x 100 P solution = X solvent P o solvent X solvent + ix solute = 1