Page 2. Base your answers to questions 7 through 9 on this phase diagram

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1 1. The normal boiling point of water is often depressed at high altitudes. Which of the following explains this phenomenon? t high altitudes, the lower atmospheric pressure equals the equilibrium water vapor pressure at a lower temperature. (B) There are fewer oxygen molecules present at high elevations. (C) Water molecules have greater average kinetic energies at higher altitudes because the pressure is lower. (D) All polar substances (such as water) have lower boiling points at higher elevations. (E) Water at this altitude has more nitrogen dissolved in it, lowering the boiling the point. 6. In the phase diagram of water, graphing pressure versus temperature, why does the equilibrium between the solid and liquid phases curve to the left? (A) The solid phase is more dense than the liquid phase. (B) An increase in pressure causes the liquid to vaporize. (C) The liquid phase is more dense than the solid phase. (D) The liquid phase has a higher vapor pressure than the solid phase. (E) At higher temperatures, the liquid is more likely to vaporize. 2. Pressure cookers are used at high altitudes to cook food faster, which of the following statements pertaining to this fact is true? (A) The cooker holds water at a constant pressure at a higher atmosphere, resulting in hotter water. (B) The cooker lowers the pressure on water causes it to boil at a higher temperature, allowing for hotter water. (C) The cooker raises the pressure on water causing it to boil at a higher temperature, allowing for hotter water. (D) The cooker forces the water to contain a higher concentration of dissolved gases, allowing for hotter water. (E) The cooker forces the water to maintain constant density, allowing for hotter water. 3. Which property is higher for any 2.0 molar aqueous solution than it is for pure water? (A) Electrical conductivity (D) Opaqueness (B) ph (E) Boiling point (C) Vapor pressure 4. The pressure and temperature at which a substance is in equilibrium between solid, liquid and gas phases is known as the (A) freezing point depression (D) triple point (B) STP (E) normal boiling point (C) osmotic pressure 5. The critical pressure of a substance is the (A) pressure above which it cannot be liquified at any temperature (B) pressure where the solid liquid and gas phases can coexist at equilibrium (C) pressure that is present at absolute zero (D) pressure at which the substance would boil at a constant temperature (E) vapor pressure of the substance at 0ºC Page 1

2 Base your answers to questions 7 through 9 on this phase diagram 7. The critical temperature of this substance is 290 o C. What is meant by the term "critical temperature"? (A) It is the temperature at which the substance can no longer exist. (B) It is the temperature above which a substance can no longer be evaporated. (C) It is the temperature above which a substance can no longer be liquified. (D) It is the temperature above which a substance can no longer be solidified. (E) It is the temperature at which all electrons enter the excited state. 8. What is the normal boiling point of the substance on the graph above? (A) 100 o C (B) 80 o C (C) 290 o C (D) 5.5 o C (E) -1.5 o C 9. What information could you NOT learn from this diagram? (A) The conditions needed for sublimation (B) The relative densities of the three phases of this substance (E) The triple point of the substance (C) The critical pressure of the substance (D) The latent heat of vaporization 10. The phase diagram for a pure substance is shown above. What is the normal melting point temperature for this substance? (A) 5.5 o C (B) 15.0 o C (C) 80.0 o C (D) o C (E) 0 o C Page 2

3 11. Which cannot be determined from the typical triple point graph? (A) The critical pressure (B) The critical temperature (C) The triple point (D) Conditions needed for sublimation (E) The heat of vaporization 12. What phase change is occuring from point A to point B? (A) Solidification (B) Condensation (C) Sublimation (D) Vaporization (E) Melting Base your answers to questions 13 and 14 on this cooling curve for a pure substance as it changes from a liquid to a solid 14. What is taking place between points A and B? (A) The substance is condensing (B) The liquid phase of the substance is cooling (C) The substance is melting (D) The substance is undergoing an endothermic process (E) The substance is becoming a solid 13. According to this curve, when is the substance solidifying? (A) Point B only (B) Point C only (C) All points between B and D (D) All points between C and D (E) All point between C and E Page 3

4 15. Look at the heating curve for a pure substance above. Which of the following is true about the substance from point D to E? (A) Kinetic energy is increasing; potential energy is decreasing (B) Kinetic energy is decreasing; potential energy is increasing (C) Kinetic energy is constant; potential energy is decreasing (D) Kinetic energy is constant; potential energy is increasing (E) Kinetic energy is increasing; potential energy is constant 16. Which are allotropes? 234 U, U euterium, Tritium (A) (B) Fe 2+, Fe 3+ (E) FeO, Fe 2 O 3 (C) O 2, O Oxygen and its allotrope ozone differ in the (A) number of atoms in the molecule (B) number of protons in the nucleus (C) number of neutrons in the nucleus (D) number of orbital electrons in an atom (E) number of principal energy levels 18. Which element has at least two common allotropic forms? (A) Calcium (D) Copper (B) Carbon (E) Sodium hromium Page 4

5 19. A sample of carbon dioxide at 10 C is heated at a constant pressure of atmospheres, as indicated by the arrow. Which phase change occurs? (A) fusing (B) boiling (C) melting (D) deposition (E) sublimation 20. Which of the following molecules has a higher boiling point than the others? (A) CO 2 (D) CH 4 (B) SO 2 (E) BF 3 6 H 6 Base your answers to questions 21 through 25 on the following types of energy. 21. (A) Lattice energy (B) Potential energy (C) Kinetic energy (D) Electromagnetic energy (E) Vaporization energy The energy required to change a substance from a liquid to a gas 22. Energy that is given off in waves and is defined by wavelength and frequency 23. Energy that is measured by (1/2)mv Energy that can be used to directly calculate (H 25. Energy that binds together ionic solids Base your answers to questions 26 through 29 on the following terms: 26. (A) Gibbs free energy (B) Entropy (C) Heat of Vaporization eposition (E) Vapor Pressure When the solid phase of a substance is in equilibrium with the gas phase, the pressure of the gas is equal to what? 27. The energy that is required in order to overcome the intermolecular forces between liquid molecules. Page 5

6 28. This quantity is equal to 0 at the freezing point. 29. The physical change of a gas to a solid 30. (a) A 3.4 g sample of a liquid is completely vaporized at its boiling point of 20ºC and a pressure of torr. The resulting vapor has a volume of 240. milliliters. Assuming the gas is ideal, what is its molecular mass. (b) At a temperature not far above the boiling point, the gas is not ideal. How does its actual molecular mass compare to that calculated in part (a)? Justify your answer. 31. (a) State two ways that real gases differ from ideal gases and how this affects the equation of state. (b) Which of the following gases would have the greatest deviation from ideal behavior. Justify your answer. F 2 CO 2 CH 4 N 2 O 3 (c) Under what conditions of temperature and pressure do real gasses most closely approximate ideal gasses? (A) (a)1. Real molecules have a finite volume. Thus making the actual volume greater than the ideal volume 2. Real gases experience IMF's thus making the real pressure less than the ideal pressure. (b) N 2 O 3 because it is the largest molecule and has the strongest intermolecular forces. (c) Low pressure and high temperature. 32. The equation of state for a real gas is (P + an 2 /V 2 )(V nb) = nrt where a and b are experimentally determined constants. (a) What properties of real gases do the constants a and b depend on. (b) Between the gases HCl and Cl 2, which would have the higher value of a, which would have the higher value of b. Justify. (c) What is one property of a gas that is affected by the constant a; how is it affected? 33. Give a scientific explanation for each of the following observed pehnomena. (a) A hydrogen filled balloon can lift more weight than a helium filled baloon of equal volume. (b) When a baloon filled with gas is allowed to sit undisturbed, its volume slowly decreases. 34. A mixture of O 2 (g), N 2 (g), and 3 grams of N 2 O 5 (s) is placed in an evacuated.600 liter container at 7ºC. The number of moles of O 2 ( g) and N 2 (g) are the same. The total pressure is 12,304 torr. (The equilibrium vapor pressure of N 2 O 5 (s) at 7ºC is 96 torr), and 3 grams of N 2 O 5 (s) is placed in an evacuated liter container at 7ºC. The number of moles of O 2 (g) and N 2 (g) are the same. The total pressure is torr. (The equilibrium vapor pressure of N 2 O 5 (s) at 7ºC is 96 torr.) The mixture is sparked, and the O 2 (g) and N 2 (g) react until one is completely consumed. Assume the only product is N 2 O 5 (s). (a) Which is the remaining reactant and how many moles of it are left? (b) Calculate the total pressure in the container at 20ºC (The equilibrium vapor pressure of N 2 O 5 (s) at 20ºC is 362 torr.) (c) Calculate the number of moles of N 2 O 5 present in the vapor. (A) (a) mol N 2 (g) (b) 1,080 torr. (c) mol. Page 6

7 35. Explain the following phenomena in molecular terms, using kinetic molecular theory or ideas about intermolecular forces. (a) A gas filled baloon would always expand when heated. (b) Though the ideal gas law predicts that a gas would have zero volume at absolute zero, as a real gas is cooled it does not reach zero volume but liquifies or solidifies first. (c) When ammonia and hydrogen iodide gas are introduced to opposite ends of a long tube nothing occurs for a while, then a white ring is observed to form closer to the hydrogen iodide side. (d) A windmill turns on a windy day. 36. A student collected a sample of helium gas by the displacement of water. The following data were collected. (a) How many atoms of He (g) are present in the sample collected? (b) How many moles of H 2 O(g) are in the sample? (c) What is the ratio of average molecular velocity between He(g) and H 2 O(g)? (d) Which one of the gases exhibits behavior closer to ideal. Explain. 37. The diagram above shows 5 identical balloons each filled with a different gas. Each is kept at a pressure of 1.0 atm and a temperature of 40ºC. (a) Which balloon has the least mass? Explain. (b) In which balloon do the particles have the least average velocity? Explain. (c) Which gas is closest to ideal? Explain (A) (a) Ne; Since each balloon contains the same number of particles, the balloon whose particles have the least mass has the least mass. (b) H 2 S; All particles are at the same temperature, and thus have the same average kinteic energy. The relation E = ½mv 2 shows that the particles with the greatest mass will have the least average velocity. (c) Ne; it contains the least number of electrons and has the lowest mass. Page 7

8 38. Four identical flasks each contain a 0.20 M solution of a different solute as follows. Flask I: NaOH Flask II: NH 4 Cl Flask III: C 3 H 7 OH Falsk IV: MgBr 2 (a) Which solution has the highest electrical conductivity? Explain. (b) Which solution has the lowest boiling point? Explain. (c) In which solution is the vapor pressure of water the greatest? Explain. (d) Which solution has the lowest ph? Explain. 39. (a) List and define 3 different ways to express the concentration of a solution. (b) For each way in part (a), indicate an experimental situation in which it would be appropriate to express concentration by this manner. 40. Two beakers, one containing pure water, and one containing a 0.10 M glucose solution are placed next to each other in a closed system. Explain in terms of chemical and or physical principles the processes that take place to bring the system to equilibrium. 41. When a sample of ethane gas in a closed container is cooled so that its absolute temperature halves, which of the following also halves? (A) The average kinetic energy of the gas molecules (B) The potential energy of the gas molecules (C) The density of the gas (D) The volume of the gas (E) The number of molecules in the gas 42. A sample of gas in a closed container is raised to double its initial pressure while remaining at constant temperature. Which of the following occurs? (A) The volume of the gas doubles. (B) The density of the gas doubles. (C) The density of the gas halves. (D) The average kinetic energy of the molecules doubles. (E) The size of the molecules doubles. 43. Two containers for gases are at the same temperature and pressure. One contains 14.0 grams of nitrogen and the other 2.0 grams of helium. Which of the following is true? (A) The volumes of the containers are the same. oth containers contain the same number of atoms. (C) The average speed of the particles in both containers is the same. (D) The density of the containers is the same. (E) The size of the helium atoms is the same as the size of the oxygen atoms. 44. A sample of mol of chlorine gas is kept at 27.0ºC and atm. What would be its pressure if the temperature was increased to 227.ºC and the volume kept the same (A) atm (D) 2.10 atm (B) atm (E) atm (C) 1.20 atm 45. A 2.70 L sample of nitrogen gas is kept at a pressure of 800. torr and 27.0ºC. what would its volume be if the pressure was increased to torr and it was cooled to -73.0ºC. (A) 1.35 L (D) 3.60 L (B) 1.80 L (E) 1.2 L (C) 2.70 L 46. What is the density of a gass that has a molar mass of 336 g/mol at STP? (A) 15 g/l (D) 168 g/l (B) 17 g/l (E) 336 g/l (C) 150 g/l 47. What is the density of oxygen gas at STP? (A) 0.7 g/l (D) 16. g/l (B) 1.4 g/l (E) 32. g/l (C) 2.5 g/l 48. An ideal gas in a sealed container is heated from 290 K to 370 K at constant volume. Which of the following DO NOT change? I. The density of the gas II. The average distance between molecules III. The average speed of the molecules. (A) I only (D) I and III only (B) III only (E) I, II, and III (C) I and II only Page 8

9 49. The pressure on a sample of gas is increased from 100 kpa to 130 kpa at constant temperature. Which of the following increases? I. The density of the gas II. The average distance between molecules III. The average speed of the molecules. (A) I only (D) I and II only (B) III only (E) I, II, and III (C) I and III only 50. At 25ºC He gas (molar mass 4.00 grams) effuses at a rate of mole per minute. What is the rate of effusion of O 2 (molar mass 32.0 grams)? (A) mole per minute (D) 0.20 mole per minute (B) mole per minute (E) 0.40 mole per minute (C) 0.10 mole per minute 51. At 25.ºC, C 2 H 6 (molar mass 30. g) effuses at a rate of 0.38 mole per minute. Which gas would have a rate of effusion approximately one-half as fast? (A) He (molar mass 4.0 g) (D) N 2 O 3 (molar mass 76. g) (B) CH 4 (molar mass 16. g) (E) Cl 2 O 3 (molar mass 119. g) (C) NO (molar mass 30. g) 52. A gas gives off J of heat at the same time that it expands from liters to liters against a pressure of atm. (1 L atm =101.0 J). What is the internal energy change of the gas? (A) J (D) J (B) J (E) J (C) J 53. The total internal energy change for a gas is J. If it expanded from liters to liters against a pressure of atm. What was the change in heat for the system? (1.00 L atm = J) (A) 3406.J (D) J (B) 2194.J (E) J (C) +606.J 54. In 1811 Avogadro calculated the formula of camphor by means of elemental chemical analysis and by measuring the density of its vapor. Avogadro found the density to be 3.84 g/l when he made the measurements at 210ºC at 1 atmosphere pressure. Which of the following is the correct formula for camphor? (A) C 10 H 14 O (D) C 10 H 18 O (B) C 10 H 16 O (E) none of the above 10 H 16 O Li + 2H 2 O 2Li + +2OH + H 2 When mol of Li is reacted with excess water at STP in the equation above, what volume of hydrogen gas is produced? (A) 2.24 L (D) 8.96 L (B) 4.48 L (E) L (C) 6.72 L 56. Which of the following gases is most like ideal? (A) He (D) CO (B) SO 2 (E) Br 2 (C) H 2 O 57. Under what conditions do gases deviate the most from ideal behavior? (A) High temperature, low pressure (B) Low temperature, low pressure (C) Low temperature, high pressure (D) High pressure only (E) High temperature only 58. The temperature of a sample of H 2 O is decreased. Which of the following can be true? (A) Volume constant, pressure increased, density constant (B) Volume constant, pressure decreased, density constant (C) Volume constant, pressure constant, density constant (D) Volume decreased, pressure constant, density increased (E) Volume decreased, pressure increased, density decreased 59. A gas has a density of 0.25 g/l at a pressure of atm and a temperature of 27. o C. What is the molar mass of the gas? (A) 0.25 g/mol (D) 38. g/mol (B) 25. g/mol (E) 75. g/mol (C) 30. g/mol 60. A gas has a density of g/l at a pressure of atm and a temperature of 127. o C. What is the molar mass of the gas? (A) 60.0 g/mol (D) 360. g/mol (B) 120. g/mol (E) 480. g/mol (C) 240. g/mol gram of propene gas occupies what volume at 147. o C and 1.00 atm? (A) L (D) 0.41L (B) L (E) 1.64 L (C) L 62. A L container at 273. o C contains 10.0 moles of neon gas. What is the pressure inside the container? (A) 27.3 atm (D) 546. atm (B) 410. atm (E) 273. atm (C) 137. atm Page 9

10 63. A 1.00 L container at 460. K contains 3.23 moles of argon gas. What is the pressure of the gas? (A) atm (D) 244. atm (B) 194. atm (E) 87.0 atm (C) 122. atm A certain first order reaction between two gases occurs at 389 K with a half-life of 24 hours. How much time is required to drop the pressure of one of the gases from 2.0 atm to 0.25 atm at 389 K? (A) 3 hours (D) 192 hours (B) 8 hours (E) 288 hours (C) 72 hours 69. A CH 4 (molar mass 16 grams) effuses at mole per minute at 289 K. At that temperature, a gas that effuses at approximately double that rate has what molar mass? (A) 4 grams (D) 32 grams (B) 8 grams (E) 64 grams (C) 16 grams The graph table above shows what happens when one mole of magnesium reacts with acid to produce one mole of H 2 (g). What is the molar volume of H 2 at 760 mmhg and 298 K using this data? (A) 22.4 L (D) 36.6 L (B) 23.3 L (E) 46.6 L (C) 25.4 L 65. The gaseous pressure in a 500 ml flask is 250 mmhg at 284 K. What is the number of moles of gas present in the flask? (A) mole (D) 143 moles (B) mole (E) 181 moles (C) 7.05 moles C 3 H 8 (g) + 5O 2 (g) 3CO 2 (g) + 4H 2 O(g) A 0.03 mol sample of C 3 H 8 is reacted with just enough O 2 to use up both reactants in a 1 L flask at 300 K. The total pressure in the flask after the reaction is complete is closest to which of the following? ( Use R = L atm mol 1 K 1 ) (A) 5.0 (D) 0.25 (B) 0.5 (E) 0.05 (C) 0.1 Base your answers to questions 71 through 74 on Questions refer to the following molecules. (A) H 2 (B) O 2 (C) Br 2 (D) N 2 (E) F Which molecule as a gas effuses the fastest? A plastic bag is massed. It is then filled with a gas which is insoluble in water and massed again. The apparent weight of the gas is the difference between these two masses. The gas is squeezed out of the bag to determine its volume by the displacement of water. What is the actual weight of the gas? (A) 0.90 g (D) 2.82 g (B) 1.02 g (E) 3.90 g (C) 1.92 g 67. The pressure of a given mass of gas varies directly with the absolute, Kelvin, temperature with the volume being kept constant. This statement best illustrates vogadro s Principle (D) Gay Lussac s Law oyle s Law (E) Charles Law ombined Gas Law 72. Which molecule has a bond order of 3? 73. Which molecule has one sigma bond and one pi bond? 74. Which molecule has the shortest bond length? Page 10

11 75. A balloon filled with 0.01 mol of hydrogen gas is kept constant at 25 degrees Celcius. If the pressure is changed from 1 atm to 1.5 atm, what is the resulting volume of the balloon? (A) 0.12 L (D) 0.27 L (B) 0.15 L (E) 0.30 L (C) 0.25 L 76. A sealed container contains mol of methane gas, mol of ethane gas, and mol propane gas. If the total pressure of the mixture is 3.00 atm, what is the partial pressure of the propane? (A) atm (D) 1.50 atm (B) atm (E) 3.00 atm (C) 1.00 atm 77. A 3.00 mole sample of a gas mixture of oxygen, nitrogen and chlorine has a total pressure of 6.00 atm. If the partial pressure of oxygen in the mixture is 1.5 atm, how much oxygen is there? (A) 3.00 mol (D) mol (B) 1.50 mol (E) mol (C) 1.00 mol 78. A gas mixture contains mol neon, mol argon and mol helium. If the partial pressure of argon is 1.00 atm, what is the total pressure of the mixture? (A) atm (D) 2.50 atm (B) atm (E) 4.00 atm (C) 1.00 atm 79. Equal masses of oxygen, nitrogen, and helium gases were sealed in a rigid container. The total pressure in the container is 1 atm. Which of the following is true about the partial pressure of the helium? (A) It is equal to the partial pressure of the oxygen. (B) It depends on the temperature of the system. (C) It depends on the shape of the container. (D) It is less than the partial pressure of the nitrogen. (E) It is greater than 0.5 atm. 80. Equal masses ideal gases X, Y, and Z are sealed in a rigid container with a total pressure of 1.0 atm. If the partial pressure of X is 0.50 atm and the partial pressure of Y is 0.30 atm, what are possible atomic masses for the 3 gases? (A) X = 5.0 g Y = 3.0 g Z = 2.0 g (B) X = 2.0 g Y = 3.0 g Z = 5.0 g (C) X = 6.0 g Y = 10. g Z = 15. g (D) X = 15. g Y = 10. g Z = 6.0 g (E) X = 10. g Y = 10. g Z = 10. g 81. Samples of F 2 and Kr gas are mixed in a rigid container. The initial partial pressure of fluorine is 1.2 atm and the partial pressure of the krypton is 0.2 atm. After all the krypton reacted, forming a solid compound, the total pressure was 0.7 atm. What is the formula for this compound? (A) KrF (D) KrF 5 (B) KrF 2 (E) KrF 7 (C) Kr 2 F A gaseous mixture containing 6.5 moles of nitrogen, 2.0 moles of chlorine, and 1.5 moles of hydrogen exerts a total pressure of 0.70 atmosphere. What is the partial pressure of the chlorine? (A) 0.07 atm (D) 0.26 atm (B) 0.10 atm (E) 0.31 atm (C) 0.14 atm 83. A gaseous mixture contains 4.5 moles hydrogen, 2.0 moles nitrogen, and 3.5 moles neon. This system exerts a total pressure of 0.80 atmosphere. What is the partial pressure of the hydrogen? (A) 0.36 atm (D) 0.61 atm (B) 0.42 atm (E) 0.65 atm (C) 0.57 atm 84. A gaseous mixture contains 4.50 moles hydrogen, 2.50 moles oxygen, and 3.00 moles argon. This system exerts a total pressure of atmosphere. What is the partial pressure of the hydrogen? (A) atm (D) atm (B) atm (E) atm (C) atm 85. Hydrogen gas is collected over water at 29 o C. The total pressure of the system is 773 torr. If the vapor pressure of water at 29 o C is 30 torr, what is the partial pressure of the hydrogen gas? (A) 803 torr (D) 753 torr (B) 30 torr (E) 773 torr (C) 743 torr 86. Find the partial pressure of Hydrogen gas collected over water at 18 o C if the the vapor pressure of water at 18 o C is 15.5 torr, and the total pressure of the sample is 745 torr. (A) torr (D) torr (B) torr (E) torr (C) 15.5 torr 87. A sealed metal tank is filled with neon gas. Which of the following does NOT occur when neon gas is pumped into the tank at a constant temperature? (A) The average speed of the neon atoms remains the same. (B) The density of neon gas inside the tank increases. (C) The average distance between molecules decreases. (D) The volume of the gas decreases. (E) The pressure inside the tank increases. Page 11

12 88. C 3 H 7 OH (s) H 2 O(g) + C 3 H 6 (g) A student places 0.05 mole of C 3 H 7 OH (s) in a 1 L vacuum flask, which is sealed and heated. The propanol decomposes completely according to the balanced equation above. If the flask's temperature is 500. K, the total pressure in the flask is closest to which of the following? (Use R = 0.08 L atm/mol K) (A) 8.0 atm (D) 2.0 atm (B) 50. atm (E) 4.0 atm (C) 25. atm 89. BCl 3 NH 3 BCl 3 + NH 3 A student places 0.10 mole of BCl 3 NH 3 in a 1 L vacuum flask, which is sealed and heated. The BCl 3 NH 3 decomposes completely according to the balanced equation above. If the flask's temperature is 375. K, the total pressure in the flask is closest to which of the following? (Use R = 0.08 L atm/mol K) (A) 6.0 atm (D) 4.5 atm (B) 1.5 atm (E) 7.5 atm (C) 3.0 atm 90. Equal numbers of moles of CO 2 (g), NH 3 (g), SO 2 (g) are placed into 3 separate identical containers. If each container has an identical pinhole leak, which of the following is true about the moles of gas remaining in each container after some time has elapsed? (A) mol CO 2 < mol NH 3 < mol SO 2 (B) mol CO 2 < mol SO 2 < mol NH 3 (C) mol NH 3 < mol SO 2 < mol CO 2 (D) mol NH 3 < mol CO 2 < mol SO 2 (E) mol SO 2 < mol CO 2 < mol NH 3 < 91. Equal numbers of moles of H 2 O(g), F 2 (g), Cl 2 (g) are placed into a single container. The container has a pinhole-sized leak (1 mm), and after 10 minutes some gas has escaped from the container. What is best reason for why there is more Cl 2 gas left in the container than any other gas? (NOTE: the molecules do not react with each other) (A) The Cl 2 molecule is too big to escape through the leak-hole (B) The rate of effusion for Cl 2 is less than than that of the other two gases l 2 is a nonpolar molecule (D) Cl 2 has the smallest S o of the three gases (E) H 2 O has the greatest rate of diffusion 92. A mixture of Cl 2 gas and and O 2 gas occupy a L container at a pressure of torr. There are 3 times as many chlorine molecules as oxygen molecules. If the oxygen gas is removed from the mixture and placed inside an identical container (temperature is constant) what is the pressure inside the new container? (A) 300. torr (D) torr (B) 600. torr (E) 400. torr (C) 900. torr 93. A student collected a sample of gas using water displacement. Which of the following measurements is necessary to determine the vapor pressure of the water in the sample? (A) The volume of the gas (B) The kinetic energy of the gas (C) The volume of the water (D) The temperature of the water (E) The water solubility of the gas 94. What is the total pressure after 1.00 mole of H 2 (g), 1.00 mole of N 2 (g), 1.00 mole of O 2 (g) and 3.00 moles of CO 2 (g), are injected into a rigid 22.4 L container at 273 K? (A) 760 mmhg (D) 9,120 mmhg (B) 2,280 mmhg (E) 63,500 mmhg (C) 4,560 mmhg 95. Which of the following is NOT an assumption of the ideal gas law ll collisions are elastic (B) There are no intermolecular forces (C) All gasses behave in the same manner (D) Particles are sizeless (E) There is no effect of the kinetic energy of particles on the equation of state 96. A rigid container filled with an ideal gas has its temperature raised from 283 K to 293 K. Which of the following increases? I. Average distance between the molecules II. Average speed of the molecules III. Density IV. Influence of particle-particle interaction (A) I only (D) I, II, and III only (B) II only (E) I, II, and IV only (C) III only 97. A rigid cylinder is filled with gas. At constant temperature, which of the following applies to the gas in the cylinder when gas is released? (A) The average kinetic energy of the gas particles increases. (B) The pressure of the gas increases. (C) The volume of the gas decreases. (D) The total number of gas molecules stays constant. (E) The total force of the gas molecules hitting the side of the container decreases. Page 12

13 98. The temperature of a sample of xenon atoms is raised from 50 o C to 90 o C. Which of the following statements is true about the average kinetic energy of the atoms? (A) The average kinetic energy does not change. (B) The average kinetic energy of the sample increased by a factor of 363/323. (C) The average kinetic energy of the sample increased by a factor of 9/5. (D) The average kinetic energy increased by a factor of 81/25. (E) More information is needed to know whether the average kinetic energy changed. 99. A balloon inflated with helium rises. Which of the following choices is the best explanation for this phenomenon? (A) The density of helium gas is less than that of the surrounding air. (B) The inside of the balloon is warmer than the outside. (C) Helium effuses through pores in the balloon. (D) Outside pressure forces the balloon upwards. (E) The cooler air surrounding the ballon pushes against the side of the balloon K 2 SO HCl 2 KCl + H 2 O +SO 2 A 2.50 sample containing potassium sulfite and potassium iodide is analyzed by adding hydrochloric acid. The sulfur dioxide formed measured ml when collected over water at 21ºC and a pressure of mm Hg. What is the percent by mass of potassium sulfite in the original sample. (The vapor pressure of water at 21ºC is 18.7 mm Hg.) 101. At 25ºC, the vapor pressure of formic acid is 43 torr and the vapor pressure of acetic acid is 35 torr. (a) When 1.5 moles of a non-volatile non electrolyte is disolved in 30. moles of formic acid, what is the vapor pressure of the solution. (b) A solution is made with 4.0 moles of acetic acid and 2.0 moles of formic acid. (i) What is the vapor pressure of the solution at 25ºC (ii) What is the percent of formic acid in the vapor (A) (a) 41 torr (b) (i) 37.7 torr (ii) 38% 102. A 5.67 gram sample of iodine heptaflouride is placed in a 3.0 liter evacuated flask and completely vaporized at 184ºC. (a) If no reaction occurs, what is the pressure in the flask. (b) Iodine heptaflouride decomposes acording to the reaction IF 7 IF 5 + F 2 If the pressure in the flask is measured to be.50 atmospheres, what is the partial pressure of the IF 7 and the IF 5 at 184ºC. Page 13

14 Answer Key 1. A 2. C 3. E 4. D 5. A 6. C 7. C 8. B 9. D 10. A 11. E 12. C 13. C 14. B 15. D 16. C 17. A 18. B 19. E 20. B 21. E 22. D 23. C 24. B 25. A 26. E 27. C 28. A 29. D 30. (a) 216 g / mol (b) The actual mass is lower. We have MM = mrt/pv, intermolecular forces make the product PV smaller and thus the calculated value too high. 31. (a)1. Real molecules have a finite volume. Thus making the actual volume greater than the ideal volume 2. Real gases experience IMF's thus making the real pressure less than the ideal pressure. (b) N 2 O 3 because it is the largest molecule and has the strongest intermolecular forces. (c) Low pressure and high temperature. 32. (a) a depends on the strength of intermolecular forces, b depends on the size of the molecules. (b) HCl would have a higher value of a. Cl 2 would have a higher value of b. (c) Boiling point, increases with increasing a. OR Vapor pressure, decreases with increasing a. 33. (a) hydrogen is less dense than helium. (b) The gas effuses through the walls of the balloon. 34. (a) mol N 2 (g) (b) 1,080 torr. (c) mol. 35. (a) Increasing the temperature of the gas increases the kinetic energy of the gas molecules, thus increasing the frequency and strength of collisions with the walls of the balloon. (b) The molecules in real gases have finite volumes. As they cool, the intermolecular forces cause them to liquify or solidify. (c) The gases slowly diffuse along the tube since they are in constant motion. The ammonia diffuses faster since it has a lower molecular mass and thus a higher velocity at constant temperature. When they mix, they react to form a white powder. (d) The gas molecules in the air carry momentum. When they strike the windmill some of this momentum is transferred. 36. (a) (b) (c).707 or 1:`2 (d) Helium, it is smaller and has a dipole moment of (a) Ne; Since each balloon contains the same number of particles, the balloon whose particles have the least mass has the least mass. (b) H 2 S; All particles are at the same temperature, and thus have the same average kinteic energy. The relation E = ½mv 2 shows that the particles with the greatest mass will have the least average velocity. (c) Ne; it contains the least number of electrons and has the lowest mass. 38. (a) IV, MgBr 2 would dissociate into the greatest number of ions. (b) III, boiling point elevation is proportional to the number of dissolved particles, C 3 H 7 OH does not dissociate. (c) III, vapor pressure decrease is proportional to the number of dissolved particles, C 3 H 7 OH does not dissociate. (d) II, NH 4 Cl forms a weakly acidic solution. 39. (a) molarity (M): moles of solute per liter of solution molality (m) : moles of solute per kilogram of solvent

15 mole fraction (X): moles of substance / total moles present (b) molarity- titration molality- freezing point depression mole fraction - vapor pressure Answer Key 66. D 67. D 68. C 40. The vapor pressure of the pure water is greater, and thus the rate of condensation in the sugar solution will be greater than the rate of 69. A evaporation. Eventually the volume of the pure water would decrease to 0, and the volume of the sugar solution would increase to ~200 ml. 70. A 41. A 42. B 43. A 44. B 45. E 46. A 47. B 48. C 49. A 50. B 51. E 52. A 53. A 54. B 55. D 56. A 57. C 58. B 59. E 60. B 61. A 62. D 63. C 64. B 65. B 71. A 72. D 73. B 74. D 75. B 76. A 77. D 78. E 79. E 80. C 81. D 82. C 83. A 84. C 85. C 86. E 87. A 88. D 89. C 90. D 91. B 92. A 93. D 94. C 95. E

16 Answer Key 96. B 97. E 98. B 99. A % 101. (a) 41 torr (b) (i) 37.7 torr (ii) 38% 102. (a) atm (b) IF atm IF atm