Multiple Choice (40%)

AP Chemistry Test (Chapter 5) Please do not write on this test thank you! Multiple Choice (40%) 1) A sealed rigid container is filled with three ideal gases: A, B and C. The partial pressure of each gas is known. The temperature and volume of the system are known. What additional information is needed to determine the masses of the gases in the container? A) The average distance traveled between molecular collisions B) The intermolecular forces C) The volume of the gas molecules D) The total pressure E) The molar masses of the gases 2) Two balloons are at the same temperature and pressure. One contains only 14 g of nitrogen and the other contains only 20 g of argon. Which one is a false statement? A) The density of the nitrogen sample is less than the density of the argon sample. B) The average speed of the nitrogen molecules is the same as the average speed of the argon molecules. C) The average kinetic energy of the nitrogen molecules is the same as the average kinetic energy of the argon molecules. D) The volume of the nitrogen balloon is the same as the volume of the argon ballon. E) The number of molecules in the nitrogen balloon is the same as the number of atoms in the argon balloon. 3) A reaction produces a gaseous mixture of CO 2, CO and H 2 O (g). The mixture is analyzed and found to contain 0.60 mol CO 2, 0.30 mol CO and 0.10 mol H 2 O (g). If the total pressure of the mixture was 0.80 atm, what was the partial pressure of the CO? A) 0.080 atm B) 0.34 atm C) 0.13 atm D) 0.24 atm E) 0.48 atm 4) Please determine the formula for a gaseous silane (Si n H 2n+2 ) if it has a density of 5.47 g/l at STP. A) SiH 4 B) Si 2 H 6 C) Si 3 H 8 C) Si 4 H 10 E) Si 5 H 12 5) A glass flask is filled at room temperature with an equal number of moles of H 2, O 2 and NO 2 gases. The gases slowly leak out through a pinhole leak in the cork of the flask. After some of the gas has effused, which one is true of the partial pressures of the gases remaining in the flask? A) H 2 < NO 2 < O 2 B) NO 2 < H 2 < O 2 C) H 2 = NO 2 = O 2 D) O 2 < NO 2 < H 2 E) H 2 < O 2 < NO 2

6) Which of the following best explains why a hot air balloon rises? A) The heat decreases the volume of the balloon; thus increasing its density. B) The heat decreases the volume of the balloon; thus decreasing its density. C) The heat increases the volume of the balloon; thus increasing its density. D) The heat increases the volume of the balloon; thus decreasing its density. 7) Which of the following conditions would be most likely to cause a gas to NOT behave ideally? I. High pressure II. High temperature III. Large volume IV. Nonpolar molecules V. Intermolecular attractions A) I, II, III, IV B) I, III, IV, V C) IV, V D) I, III, V E) I, V 8) N 2 gas was collected over water at 25 o C. If the vapor pressure of water at 25 o C is 23 mm Hg and the atmospheric pressure is 781 mm Hg, what is the partial pressure of the N 2 gas? A) 23 mm Hg B) 46 mm Hg C) 551 mm Hg D) 735 mm Hg E) 758 mm Hg 9) A gas sample is confined to a 5-L container. Which one will occur if the temperature of the container is increased? I. The kinetic energy of the gas will increase. II. The pressure of the gas will increase. III. The density of the gas will increase. A) I B) I, II, III C) I, II D) I, III E) II, III 10) What is the pressure in this stoppered flask if the atmospheric pressure is 765 mm Hg? 27 mm Hg A) 694 mm Hg B) 738 mm Hg C) 792 mm Hg D) 802 mm Hg

11) Which one is true? A) As the temperature of water increases, its vapor pressure increases because more B) As the temperature of water increases, its vapor pressure decreases because more C) As the temperature of water increases, its vapor pressure increases because less D) As the temperature of water increases, its vapor pressure decreases because less 12) Which one is false? A) Some gases exist at 0 o C. B) Some gases exist at 0 K. C) Some liquids exist at 0 o C. D) Solids exist at 0 K. E) Some solids exist at 0 o C. 13) Which one causes the bends as you ascend from a deep dive? A) Decreased external pressure causes increased solubility of gas in your blood. B) Increased external pressure causes increased solubility of gas in your blood. C) Decreased external pressure causes decreased solubility of gas in your blood. D) Increased external pressure causes decreased solubility of gas in your blood. 14) If you pack a sealed bottle of suntan lotion in your suitcase in Houston (sea level) & then fly to Colorado for a fun-filled ski trip, which one are you likely to observe when you arrive at the ski resort? A) The bottle will bulge inward & lotion will squirt out when you open it. B) The bottle will bulge inward & air will rush in when you open it. C) The bottle will bulge outward & lotion will squirt out when you open it. D) The bottle will bulge outward & air will rush in when you open it. 15) Which one would be most likely for H 2 O (l)? A) It can reach 115 o C at 1.5 atm. B) It can reach 115 o C at 0.8 atm. C) It can reach 115 o C at 1 atm. D) It can reach 100 o C at 0.8 atm. E) It can only reach 95 o C at 1.5 atm. 16) A beaker of water at room temperature (22 o C) is placed into a small, closed environment where the atmospheric pressure is 0 atm. Which one will occur? A) The water will boil until the vapor pressure prevents the liquid from boiling further. B) The water will boil until all the water has vaporized & the beaker is empty. C) The water molecules will not have enough kinetic energy to vaporize. D) The water will begin to boil when the vapor pressure increases. E) The water will only boil when heat is added to it.

17) The Lake Nyos tragedy is a sad example of which gas law? A) Charles B) Henry C) Boyle D) Graham E) Dalton 18) Which one is an example of Charles s Law? A) The pressure inside your lungs is the sum of the partial pressures of nitrogen, oxygen & carbon dioxide gases. B) Bubbles of gas exhaled by a diver at the bottom of the ocean expand as they rise to the surface of the ocean. C) Tires expand on a hot, August day in Texas. D) The pressure inside a light bulb increases as it gets hot. E) Perfume diffuses through the air. 19) A gas sample is confined to a rigid 5-L metal tank. Which one will occur if more gas is added to the tank? I) The pressure of the gas will increase. II) The volume of the tank will decrease. III) The temperature of the gas will increase. IV) The density of the gas will increase. A) I, II, V B) II, IV, V C) III, IV D) I, III, IV E) None of these will occur. 20) Which one occurs as the external pressure is increased on a sample of gas? A) Temperature and density increase. B) Temperature and density decrease. C) Temperature increases and density decreases. D) Temperature decreases and density increases. Problems (60%) Please show all your work for any credit. 1) A 1.375-g sample of impure Mn 2 (CO 3 ) 5 is heated to decompose the Mn 2 (CO 3 ) 5. 39.25 ml CO 2 is collected over water at a temperature of 30.00 o C. The gas is collected at an atmospheric pressure of 745 torr. Water has a vapor pressure of 55 torr at 40.00 o C. What is the % Mn 2 (CO 3 ) 5 in the original impure sample? Mn 2 (CO 3 ) 5 Mn 2 O 5 + 5 CO 2 2) 2 C 2 H 6 (g) + 2 NH 3 (g) + 3 O 2 (g) 2 C 3 H 3 N (g) + 6 H 2 O (l) What PO 2 is necessary to produce 1.88 g C 3 H 3 N in a 500.00-ml flask at 30.00 o C?

3) What is the molar mass of this gas? Mass of Erlenmeyer Flask Mass of Erlenmeyer Flask + Gas Mass of Gas Volume of Erlenmeyer Flask Temperature of Gas in Flask Barometric Pressure 153.255 g 153.968 g 159.38 ml 182 o C 782 torr 4) What is the total pressure in this flask after the stopcock is opened & the gases are allowed to mix at a constant temperature? 1.33 L N 2 2.71 L O 2 1.57 atm 0.85 atm 5) Air bags are activated when a severe impact causes a steel ball to compress a spring and electrically ignite a detonator cap. This causes sodium azide to decompose explosively according to the following reaction: 2 NaN 3 (s) 2 Na (s) + 3 N 2 (g) What mass of NaN 3 (s) must be reacted in order to inflate an air bag to 85.0 L if the air temperature inside the car is 22.0 o C with an atmospheric pressure of 773 mm Hg? 6) A 1.000-g sample of a gaseous hydrocarbon occupies 223.863 ml at 187 o C and 1.22 atm. The sample is burned in a combustion chamber (assume complete combustion) to produce 3.183 g CO 2 and 1.173 g H 2 O. What is the molecular formula of this gaseous hydrocarbon?

Problems (60%) #2 Please show all your work for any credit. 1) A 25.241-g sample of impure Al 2 (CO 3 ) 3 is heated to decompose the Al 2 (CO 3 ) 3. 70.95 ml CO 2 is collected over water at a temperature of 30.00 o C. The gas is collected at an atmospheric pressure of 775 torr. Water has a vapor pressure of 51 torr at 30.00 o C. What is the % Al 2 (CO 3 ) 3 in the original impure sample? Al 2 (CO 3 ) 3 Al 2 O 3 + 3 CO 2 2) 2 C 2 H 6 (g) + 2 NH 3 (g) + 3 O 2 (g) 2 C 3 H 3 N (g) + 6 H 2 O (l) During an experiment, a chemistry student observes that this reaction produces 3.497 g H 2 O in a 500.00-ml flask at 20.00 o C. What is PC 3 H 3 N in the flask? 3) What is the molar mass of this gas? Mass of Erlenmeyer Flask Mass of Erlenmeyer Flask + Gas Mass of Gas Volume of Erlenmeyer Flask Temperature of Gas in Flask Barometric Pressure 174.3300 g 174.7372 g 162.35 ml 79.55 o C 728 torr 4) What is the total pressure in this flask after the stopcock is opened & the gases are allowed to mix at a constant temperature? 0.400 mol N 2 0.300 mol O 2 1.22 atm 1.15 atm 5) Air bags are activated when a severe impact causes a steel ball to compress a spring and electrically ignite a detonator cap. This causes sodium azide to decompose explosively according to the following reaction: 2 NaN 3 (s) 2 Na (s) + 3 N 2 (g) If 20.0 g of NaN 3 is ignited, what volume will the inflated air bag have if the air temperature inside the car is 22.0 o C with an atmospheric pressure of 773 mm Hg? 6) In an experiment, a 5.000-g sample of a gaseous hydrocarbon is burned in a combustion chamber (assume complete combustion) to produce 15.684 g CO 2 and 6.422 g H 2 O. In another experiment, a different 2.000-g sample of the gaseous hydrocarbon is analyzed. It occupies 105.94 ml at 195 o C and 836 mm Hg. What is the molecular formula of this gaseous hydrocarbon?

AP Chemistry Test (Chapter 5) Name Multiple Choice (40%) 1) 11) 2) 12) 3) 13) 4) 14) 5) 15) 6) 16) 7) 17) 8) 18) 9) 19) 10) 20) Problems (60%) Please show all your work for any credit.