CHAPTER 12 GASES AND THEIR BEHAVIOR

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1 Chapter 12 Gases and Their Behavior Page 1 CHAPTER 12 GASES AND THEIR BEHAVIOR Which of the following represents the largest gas pressure? (a) 1.0 atm (b) 1.0 mm Hg (c) 1.0 Pa (d) 1.0 KPa Nitrogen gas has a pressure of 452 mm Hg. This pressure in atmospheres is (a) 4.52 atm (b) atm (c) atm (d) 1.68 atm You have O 2 gas with a pressure of 0.32 atm. What is the gas pressure in mm Hg? (a) 240 mm Hg (b) 0.24 mm Hg (c) mm Hg (d) 24 mm Hg The pressure of the atmosphere on a nice day is 751 mm Hg. What is this pressure in atmospheres? (a) atm (b) 7.51 atm (c) atm (d) 1.01 atm What are standard temperature and pressure (STP) conditions for gas law problems? (a) 760 atm, 0 o C (b) 1 mm Hg, 273 o C (c) 760 mm Hg, 273 K (d) 760 atm, 0 K Under conditions of standard temperature and pressure (STP), 1.00 mole of any gas occupies a volume of liters. (a) 22,400 (b) 273 (c) 22.4 (d) If the temperature of a confined gas sample is doubled, while the volume is held constant, what will happen to the pressure? (a) It will double. (b) It will be four times as large. (c) It will be half as large (d) Cannot be determined with information here If the pressure of a confined gas sample doubled, while the volume was held constant, what happened to the temperature? (a) It doubled. (b) It went up by a factor of four. (c) It halved. (d) Cannot be determined with information given Avogadro stated that equal volumes of gases under the same conditions of temperature and pressure have equal. (a) numbers of molecules (b) numbers of grams (c) molar masses (d) none of these

2 Chapter 12 Gases and Their Behavior Page Which of the following gas samples contains the greatest mass of gas molecules? (a) 1.0 liter of He at STP (b) 1.0 liter of Xe at STP (c) 1.0 liter of H 2 at STP (d) All three are the same A sample of a certain gas has a volume of 222 ml at 695 mm Hg and 0 o C. What would be the volume of this same sample of gas if it were measured at 333 mm Hg and 0 o C? (a) 894 ml (b) 657 ml (c) 463 ml (d) 359 ml A sample of a certain gas has a volume of 415 ml at 725 mm Hg and 0 o C. What would be the volume of this same sample of gas if it were measured at STP? (a) 581 ml (b) 435 ml (c) 396 ml (d) 301 ml The volume of a certain gas sample is 1150 ml at a temperature of 25 o C. At what temperature would that same gas sample have a volume of L if the pressure and mass of gas were held constant? (a) o C (b) 124 o C (c) 248 o C (d) 397 o C The volume of a certain gas sample is 235 ml at a temperature of 25 o C. At what temperature would that same gas sample have a volume of 310. ml, if the pressure and mass of gas were held constant? (a) o C (b) 33.1 o C (c) 69.4 o C (d) 120. o C A sample of a certain gas has a volume of 452 ml at 711 mm Hg and 26 o C. What would be the volume of this same sample of gas if it were measured at STP? (a) 386 ml (b) 442 ml (c) 462 ml (d) 530 ml A sample of N 2 is contained in a 255 ml flask at 24 C; its pressure is 45.6 mm Hg. If the gas is transferred to a 750. ml flask, and the temperature is now 35 C, what is the pressure of the gas? (a) 16.1 mm Hg (b) 139 mm Hg (c) 15.0 mm Hg (d) 22.6 mm Hg A sample of neon gas is contained in a 265 ml flask at 0.0 C; its pressure is 432 mm Hg. If the gas is transferred to a new flask at room temperature (25.0 C), where its pressure is now 355 mm Hg, what is the volume of the new flask? (a) 295 ml (b) 238 ml (c) 352 ml (d) 8060 ml What volume is occupied by moles of oxygen gas at a pressure of 555 mm Hg and a temperature of 55.0 o C? (a) atm (b) L (c) 1.31 L (d) 7.82 L

3 Chapter 12 Gases and Their Behavior Page What is the pressure exerted by 12.5 grams of carbon dioxide gas placed in a 10.0 L container at a temperature of 55.0 o C? (a) 7.65 atm (b) 1.31 atm (c) atm (d) atm What is the pressure exerted by grams of sulfur dioxide gas placed in a 250. ml container at a temperature of 25.0 o C? (a) atm (b) atm (c) 1.09 atm (d) 1.50 atm What volume is occupied by 4.00 grams of carbon dioxide gas at a pressure of atm and a temperature of 25.0 o C? (a) L (b) 2.28 L (c) 19.1 L (d) 22.8 L What volume is occupied by 1.80 grams of sulfur dioxide gas at a pressure of 2.60 atm and a temperature of 25.0 o C? (a) L (b) L (c) 28.1 L (d) 264 L Assume you place g of hexane gas (C 6 H 14 ) in the cylinder of an automobile engine. The cylinder has a volume of 250. cm 3 and the temperature is 250 o C. What is the pressure of the gas? (a) atm (b) 1.43 atm (c) 2.99 atm (d) 257 atm What is the molar mass of an unknown gas if the density of that gas is grams/liter at a pressure of atm and a temperature of 25 o C? (a) 2.35 g/mole (b) 28.0 g/mole (c) 53.2 g/mole (d) 64.0 g/mole What is the molar mass of an unknown gas if the density of that gas is grams/liter at a pressure of 71 mm Hg and a temperature of 25 o C? (a) 5.71 g/mole (b) 15.9 g/mole (c) 44.0 g/mole (d) 190 g/mole What is the molar mass of an unknown gas if 1.60 grams of that gas occupies a volume of 2.24 L at STP? (a) 16.0 g/mole (b) 35.8 g/mole (c) 81.0 g/mole (d) 160 g/mole What is the molar mass of an unknown gas if 1.92 grams of that gas occupies a volume of 673 ml at STP? (a) 57.7 g/mole (b) 63.9 g/mole (c) 112 g/mole (d) 351 g/mole

4 Chapter 12 Gases and Their Behavior Page The volume of a certain gas sample is 235 ml when collected over water at a temperature of 25 o C and a pressure of 698 mm Hg. What will be the volume of this gas sample when measured dry at standard pressure? The vapor pressure of water at this temperature is 23.8 mm Hg. (a) 197 ml (b) 191 ml (c) 223 ml (d) 265 ml A sample of oxygen gas collected by displacement of water at 40.0 o C and a pressure of 691 mm Hg has a volume of 534 ml. Calculate the volume that this sample of oxygen will occupy when dry under standard conditions of temperature and pressure. The vapor pressure of water is 55.3 mm Hg at 40.0 o C. (a) 591 ml (b) 531 ml (c) 443 ml (d) 390 ml The empirical formula of a certain hydrocarbon is CH 2. When moles of this hydrocarbon is completely combusted with excess oxygen, it is observed that 8.40 liters of CO 2 gas is produced at STP. What is the molecular formula of the unknown hydrocarbon? (a) CH 2 (b) C 2 H 4 (c) C 2 H 3 (d) C When a certain unknown hydrocarbon is completely combusted with excess oxygen, it is observed that 1.12 L of H 2 O gas and 3.36 L of CO 2 are produced at STP. What is the empirical formula of the unknown hydrocarbon? (a) CH 2 (b) C 2 H 4 (c) C 2 H 3 (d) C 4 H The empirical formula of a certain hydrocarbon is CH 2. When moles of this hydrocarbon is completely combusted with excess oxygen, it is observed that 11.2 L of H 2 O gas is produced at STP. What is the molecular formula of the unknown hydrocarbon? (a) C 2 H 4 (b) C 2 H 3 (c) C 3 (d) C 4 H If the temperature and pressure are kept constant during the process, how many liters of TiCl 4 gas will be produced when 20.0 L of chlorine react with titanium according to the reaction Ti(s) + 2 Cl 2 (g) TiCl 4 (g)? (a) 5.00 L (b) 10.0 L (c) 20.0 L (d) 40.0 L If the temperature and pressure are kept constant during the process, how many liters of chlorine must be reacted with titanium to produce 20.0 L of TiCl 4 gas according to the reaction Ti(s) + 2 Cl 2 (g) TiCl 4 (g)? (a) 10.0 L (b) 20.0 L (c) 40.0 L (d) 22.4 L

5 Chapter 12 Gases and Their Behavior Page In a certain process, ammonia gas decomposes according to the equation 2 NH 3 (g) N 2 (g) + 3 H 2 (g) If 30.0 L of nitrogen is formed at STP, how many liters of hydrogen will be produced (also measured at STP)? (a) 15.0 L (b) 30.0 L (c) 90.0 L (d) L Ammonia gas is synthesized according to the balanced equation N 2 (g) + 3 H 2 (g) 2 NH 3 (g) If 15.0 liters of nitrogen are reacted with an excess of hydrogen, how many liters of ammonia will be produced? Assume all gas volumes are measured at the same temperature and pressure. (a) 5.00 L (b) 10.0 L (c) 15.0 L (d) 30.0 L What is the pressure in atmospheres of a gas mixture that consists of moles of nitrogen and moles of oxygen in a 1250 ml container at 0 o C? (a) atm (b) atm (c) 1.79 atm (d) 8.97 atm What is the pressure in atmospheres of a gas mixture that consists of 8.80 grams of nitrogen and 8.80 grams of carbon dioxide in a 2.01 liter container at 27 o C? (a) 6.30 atm (b) 3.85 atm (c) 2.45 atm (d) atm The total pressure is 5.11 atmospheres for a gas mixture that consists of moles of carbon dioxide and an unknown quantity of methane (CH 4 ) in a 2.59 liter container at 27 o C. How many grams of methane are in this mixture? (a) grams (b) 10.1 grams (c) 8.61 grams (d) 3.70 grams For a given sample of gas molecules, the average kinetic energy depends only on the value of the (a) pressure (b) temperature (c) volume (d) moles The assumptions of the kinetic molecular theory are most likely to be incorrect for gases under which of the following combinations of conditions? (a) high temperature, high pressure (b) high temperature, low pressure (c) low temperature, high pressure (d) low temperature, low pressure Van der Waals's equation includes terms that are intended to correct for which of the following aspects for non-ideal gas behavior? (Choose the best possible answer.) (a) The volume of real gas molecules is small but not negligible. (b) There are intermolecular attractions in real gases. (c) Van der Waals's equation corrects for both volume of gas molecules and intermolecular attractions. (d) Van der Waals's eqn. corrects for neither the volume of gas molecules nor intermolecular attractions.

6 Chapter 12 Gases and Their Behavior Page What is the rms speed of nitrogen molecules at 0 o C? (a) 15.6 m/s (b) 49.0 m/s (c) 493 m/s (d) 517 m/s What is the rms speed of helium molecules at 25 o C? (a) 43.1 m/s (b) 135 m/s (c) 598 m/s (d) 1360 m/s In a certain experiment the rate of diffusion of a certain unknown gas is found to be 1.47 times as fast as that of hydrogen chloride gas. What is the molar mass of the unknown gas? (a) 617 g/mole (b) 78.9 g/mole (c) 24.8 g/mole (d) 16.9 g/mol : deleted Diborane, B 2, burns in air according to the equation B 2 (g) + 3 O 2 (g) B 2 O 3 (s) + 3 H 2 O(g) (i) There are three gases involved in the reaction above. Place them in order of increasing average velocity. (a) B 2 < O 2 < H 2 O (b) H 2 O < O 2 < B 2 (c) O 2 < H 2 O < B 2 (d) O 2 < B 2 < H 2 O (ii) If you burn a 1.49 g sample of B 2, and if you collect the water vapor in a 4.25 L flask at 30 o C, what will the pressure of H 2 O(g) be in the flask? (a) 120 mm Hg (b) 240 mm Hg (c) 360 mm Hg (d) 720 mm Hg Diborane reacts with O 2 to give boric oxide and water vapor. B 2 (g) + 3 O 2 (g) B 2 O 3 (s) + 3 H 2 O(g) If you mix B 2 and O 2 in the correct stoichiometric ratio, and if the total pressure of the mixture is 200. mm Hg, the partial pressure of the gases are (a) P(B 2 ) = 50. mm Hg and P(O 2 ) = 150. mm Hg (b) (c) (d) P(B 2 ) = 150. mm Hg and P(O 2 ) = 50. mm Hg P(B 2 ) = 100. mm Hg and P(O 2 ) = 100. mm Hg P(B 2 ) = 75 mm Hg and P(O 2 ) = 125 mm Hg Assume you place g of a gaseous compound in a L flask. It exerts a pressure of atm at 30 o C. What is the correct formula of the compound? (a) C 2, ethane (b) C 2 H 4, ethene (c) C 2 H 2, ethyne (d) C 6, benzene

7 Chapter 12 Gases and Their Behavior Page One way to analyze a metal carbonyl, one of a general class of compounds with the general formula M x, is to heat it in a closed flask. The CO is evolved in the process and can be collected, the moles of CO being related to the formula of the metal carbonyl present. To find the formula of a compound of iron and CO, you heat g of the compound and find that the evolved CO has a pressure of 469 mm Hg in a 250. ml flask at 22.0 o C. Fe(CO) x + heat Fe(s) + x CO(g) What is the formula of the iron carbonyl we have analyzed? (a) Fe(CO) 2 (b) Fe(CO) 3 (c) Fe(CO) 5 (d) Fe(CO) To determine the molecular formula for the boron-hydrogen compound, you place g of the gaseous compound in a L flask. It exerts a pressure of 325 mm Hg at 22 o C. What is the correct molecular formula of the compound? (a) B 2 (b) B 2 H 5 (c) B 4 H 10 (d) B 5 H Ethylenediamine, whose empirical formula is CH 2 NH 2, is a widely used compound. Assume that 95 mg of ethylenediamine in the gas phase has a pressure of 235 mm Hg in a 125 ml flask at 25 C. This means the molecular formula for ethylenediamine is (a) CH 2 NH 2 (b) C 2 H 4 (NH 2 ) 2 (c) C 3 (NH 2 ) 3 (d) None of the above Cobalt forms several compounds with carbon monoxide, among them Co 2 (CO) 8 (molar mass = g/mol). If you heat the compound in a vacuum it will decompose to the metal and CO. Co 2 (CO) 8 (s) 2 Co(s) + 8 CO(g) (i) (ii) Assume that the CO isolated from the reaction above was collected at 100. C in a 800. ml flask where it had a pressure of 180. mm Hg. What will the pressure be if you move the gas to a 500. ml flask and cool it to room temperature, 25 C? (a) P new = (180.)(500./800.)(373/298) (b) P new = (180.)(800./500.)(298/373) (c) P new = (180.)(800./500.)(373/298) (d) P new = (180.)(800./500.)(25/100.) If you begin with g of Co 2 (CO) 8, and you trap the CO gas in a 450. ml flask at 150. C, what will be the pressure of the gas? (a) 25.7 mm Hg (b) 33.9 mm Hg (c) 95.0 mm Hg (d) 206 mm Hg When ignited, ammonium dichromate decomposes in a fiery display. (NH 4 ) 2 Cr 2 O 7 (s) N 2 (g) + 4 H 2 O(g) + Cr 2 O 3 (s) If 15.0 g of ammonium dichromate (molar mass = g/mol) are used and if the gases from this reaction are trapped in a 15.0-L flask at 25 C, what is the total pressure of all gases in the flask? (a) 74 mm Hg (b) 485 mm Hg (c) 369 mm Hg (d) 737 mm Hg

8 Chapter 12 Gases and Their Behavior Page Equal masses of helium and neon are placed in separate containers of equal volume at the same temperature. (i) Pressures of the gases. (a) The pressure of helium is greater than the pressure of neon. (b) The pressure of neon is greater than the pressure of helium. (c) The pressures of the gases are the same. (ii) Numbers of atoms. (a) There are more atoms of helium than of neon. (b) There are more atoms of neon than of helium. (c) There are as many atoms of helium as there are of neon. (iii) Energies of the atoms. (a) The average energy of the helium atoms is greater than that of the neon atoms. (b) The average energy of the neon atoms is greater than that of the helium atoms. (c) The average energy of the helium atoms is the same as that of the neon atoms You have a sample of CO 2 in a flask (A) with a volume of 265 ml. At 22.5 C, the pressure of the gas is mm Hg. To find the volume of another flask (B), you move the CO 2 to that flask and find that its pressure is now 94.3 mm Hg at 24.5 C. What is the volume of flask B? (a) 184 ml (b) 365 ml (c) 381 ml (d) 386 ml You have a mixture of helium and hydrogen gas in a flask at room temperature. The pressure of He is 150 mm Hg and that of H 2 is 25 mm Hg. If you have 0.56 g of He, how many grams of H 2 are present? (a) g H 2 (b) g H 2 (c) 0.14 g H 2 (d) 0.17 g H A hydrocarbon with a general formula of C x H y is 92.26% carbon. Experiment shows that g of the hydrocarbon fills a 185 ml flask at 23 C with a pressure of 374 mm Hg. What is the molecular formula of the compound? (a) C 2 H 4 (b) C 5 (c) C 6 (d) C 7 H 8

9 Chapter 12 Gases and Their Behavior Page Ethane, C 2, burns in air according to the equation 2 C 2 (g) + 7 O 2 (g) 4 CO 2 (g) + 6 H 2 O(g) (i) There are four gases involved in this reaction. Place them in order of increasing velocity at 25 C. (a) C 2 < O 2 < CO 2 < H 2 O (b) CO 2 < H 2 O < C 2 < O 2 (c) CO 2 < O 2 < C 2 < H 2 O (d) H 2 O < O 2 < CO 2 < C 2 (ii) (iii) If you burn 2.00 g of C 2 in excess oxygen, and collect the reaction products (CO 2 and H 2 O) in a 15.0 L flask at 25 C, what is the total pressure of the gases (in mm Hg) in the flask? (a) 56 mm Hg (b) 168 mm Hg (c) 224 mm Hg (d) 413 mm Hg You have a mixture of C 2 and O 2 in a 5.0 L flask at 25 C. The pressure of C 2 is 20 mm Hg and that of O 2 is 85 mm Hg. After the C 2 and O 2 react as completely as possible, what is the total pressure of the gas mixture (the products and any remaining reactants) in the 5.0 L flask at 25 C? (a) 20 mm Hg (b) 85 mm Hg (c) 105 mm Hg (d) 115 mm Hg A gaseous xenon fluoride can be prepared by shining light on a mixture of Xe and F 2 gases. Assume that xenon gas was added to a 0.25-L flask until its pressure was 0.12 atm at 0.0 C. Fluorine gas was then added until the total pressure was 0.36 atm at 0.0 C. After the reaction was complete, the xenon had been consumed completely and the total pressure of the gases remaining in the flask was still 0.36 atm at 0 C. What is the empirical formula of compound prepared from Xe and F 2? (a) XeF (b) XeF 2 (c) XeF 4 (d) XeF To find the formula of a transition metal carbonyl, a family of compounds having the general formula M x, you can heat the solid compound in a vacuum to produce solid metal and CO gas. You heat g of Cr x Cr x (s) x Cr(s) + y CO(g) and find that the CO evolved has a pressure of 369 mm Hg in a 155 ml flask at 27 C. What is the empirical formula of Cr x? (a) Cr(CO) 3 (b) Cr(CO) 4 (c) Cr 2 (CO) 5 (d) Cr(CO) 6

10 Chapter 12 Gases and Their Behavior Page If you react iron with aqueous HCl, you observe the following reaction Fe(s) + 2 HCl(aq) FeCl 2 (aq) + H 2 (g) (i) If you begin with 10.0 g of iron, what is the theoretical yield of FeCl 2? (a) 12.7 g (b) 22.7 g (c) 11.3 g (d) g (ii) (iii) Again beginning with 10.0 g of Fe, how many milliliters of 2.60 M HCl would you need for complete reaction? (a) 20. ml (b) 69 ml (c) 138 ml (d) 276 ml If the H 2 gas from the reaction of 10.0 g of iron with excess HCl(aq) is collected in a 15.0 L flask at 25 C, what is the pressure of the dried gas in the flask? (a) 16.0 mm Hg (b) 18.6 mm Hg (c) 222 mm Hg (d) 384 mm Hg Two balloons, both at the same temperature, each contain gas at the same pressure. One balloon, filled with argon (Ar), has a volume of 1.0 L. The other, filled with neon (Ne), has a volume of 1.25 L. (i) (ii) Which balloon contains the greater number of atoms? (a) Argon (b) Neon (c) The number of atoms is the same in the two balloons. Which balloon contains the greater mass of gas? (a) Argon (b) Neon (c) The number of grams of gas is the same in the two balloons Dichlorodimethylsilane is made by the reaction below, which is carried out at high temperature and in the presence of a catalyst. Si(s) + 2 CH 3 Cl(g) (CH 3 ) 2 SiCl 2 (g) Assume you place mole of solid silicon in a 6.56 L flask with CH 3 Cl having a pressure of 485 mm Hg at 25 C. What is the pressure in the flask (also at 25 C) on completion of the reaction? (a) 970 mm Hg (b) 685 mm Hg (c) 485 mm Hg (d) 343 mm Hg Disulfur decafluoride, S 2 F 10, can be made by shining light on a mixture of SClF 5 and H 2. 2 SClF 5 (g) + H 2 (g) S 2 F 10 (g) + 2 HCl(g) Assume you mix the reactants in a 500. ml flask at 25 C. Their pressures are both 60. mm Hg. If the reaction goes to completion, what is the total pressure in the flask after reaction at 25 C? (a) 60. mm Hg (b) 90. mm Hg (c) 120 mm Hg (d) 180 mm Hg

11 Chapter 12 Gases and Their Behavior Page Chlorine trifluoride is made by reacting chlorine and fluorine. Cl 2 (g) + 3 F 2 (g) 2 ClF 3 (g) Assume you mix g of Cl 2 with 1.00 g of F 2 in a 258 ml flask at 23 C. What is the total pressure of gas (any remaining reactant gas plus the product) in the 258-mL flask at 23 C after reaction? (a) 1.65 atm (b) 1.76 atm (c) 1.88 atm (d) 1.53 atm Assume you have a glass tube 50. cm long. Some NH 3 (g) is allowed to diffuse along the tube from one end and some HBr(g) diffuses along the tube from the opposite end. At what distance along the tube will the gases meet and react to form solid NH 4 Br? solid NH 4 Br HBr gas NH gas 3 (a) (b) (c) (d) NH 3 moves 16 cm and HBr moves 34 cm HBr and NH 3 both move 25 cm and meet in the middle NH 3 moves 40. cm and HBr moves 10. cm NH 3 moves 34 cm and HBr moves 16 cm Iron forms a series of compounds of the type Fe x. If you heat the compounds in air, they decompose to Fe 2 O 3 and CO 2 gas. Fe x + excess O 2 (g) x/2 Fe 2 O 3 (s) + y CO 2 (g) (i) You isolate the CO 2 gas from heating in a g sample of Fe x in a 1.50 L flask at 25 C. The pressure of the CO 2 is 44.9 mm Hg. How many moles of CO 2 were isolated? (a) 27.5 mol (b) mol (c) mol (d) mol (ii) What is the formula of Fe x? (a) Fe(CO) 5 (b) Fe 2 (CO) 9 (c) Fe 3 (CO) 12 (iii) You have a 1.0 L flask containing 10.0 g each of the gases in the reaction above, O 2 and CO 2, at 25 C. The partial pressures of the gases are: (a) P(CO 2 ) > P(O 2 ) (b) P(O 2 ) > P(CO 2 ) (c) P(CO 2 ) = P(O 2 )

12 Chapter 12 Gases and Their Behavior Page 12 ANSWERS CHAPTER a 11. c 21. b 2. b 12. c 22. b 3. a 13. b 23. c 4. c 14. d 24. b 5. c 15. a 25. d 6. c 16. a 26. a 7. a 17. c 27. b 8. a 18. d 28. b 9. a 19. c 29. d 10. b 20. d 30. d 31. c 41. c 51. b 32. d 42. c 52. c 33. b 43. c 53. c 34. c 44. d 54. b 35. c 45. d 55. b, d 36. d 46. a 56. c 37. d 47. b 57. a, a, c 38. a 48. c 58. d 39. d 49. d, d 59. b 40. b 50. a 60. c 61. c, d, d 66. d 62. b 67. c 63. d 68. b 64. b, c, c 69. d 65. b, a 70. c, a, b