Alícia Rosa EXERCISES Gas Laws Chooise the correct answer 1 Atmospheric pressure at an altitude of 10 km is 2.1x10 2 mm. What is the pressure in atmospheres at 10 km? 1.6x10 5 atm 3.6 atm 0.28 atm 2 Atmospheric pressure in cities that have an altitude of about a mile, such as Denver and Reno, typically have an atmospheric pressure of about 6.4x10 2 torr. What is the pressure in atmospheres? 0.84 atm 1.2 atm 4.9x10 5 atm 1.0 atm 3 A water aspirator is capable of decreasing the pressure in the system down to the vapor pressure of water. At 20 o C, the vapor pressure of water is 0.023 atm. What pressure will the aspirator produce in torr (or mm Hg )? 3.0x10-5 torr 17 torr 3.3x10 4 torr 760 torr 4 Liquid nitrogen boils at -196 o C. What is this temperature on the Kelvin scale? 469 K 77 K -469 K
5 For the gas law problems that follow, assume that the gases behave ideally and that variables that are not stated are constant for the experiment described. The temperature of 2.0 liters of a gas at 25 o C is raised to 100 o C. What is the new volume of the gas? 8.0 L 2.0 L 2.5 L 6 The volume of a gas maintained at constant pressure halves when cooled. What is the relationship of the new temperature to the original temperature? The Celsius temperature halved. The Celsius temperature halved. The Kelvin temperature doubled. The Kelvin temperature halved. 7 Ignoring the stretching forces in the rubber, what should the volume of a 1.5 liter balloon at 20 o C be after it is submerged in liquid nitrogen (see problem #4)? 0.39 L 0.15 L 5.7 L 8 In practice when the experiment in #7 is performed, the volume of the balloon decreases to a volume that is considerably lower than the calculated answer and actually approaches a volume close to 0.0 L. Explain this observation. Air does not behave ideally at any temperature. Charles' law is incorrect. The air liquifies. 9 The pressure on a 25.5 ml volume of gas is increased from 695 mm to 755 mm while constant temperature is maintained. What is the new volume of the gas? 27.7 ml 23.5 ml 25.5 ml
10 The pressure on a 0.850 L volume of gas is decreased from 1.00 atm to 25.0 torr while constant temperature is maintained. What is the new volume of the gas? 21.2 L 0.0340 L 0.0280 L None of the previous answers 11 The volume of a gas stayed the same when the temperature was changed from 116 K to 464 K. What was the relationship of the final pressure to the original pressure? The pressure quadrupoled. The final pressure was 1/4 of the the original pressure. The pressure stayed constant. 12 The temperature of a 0.50 L sample of gas at 27 o C is changed (at constant pressure) to make the final volume of the gas 750 ml. What is the final temperature of the system? 177 o C 450 o C 40 o C 200 K 13 If a diver releases a 0.250 liter bubble of gas and a person at the surface (assume atmospheric pressure and no change in temperature) measures the volume of the bubble as 0.750 liters, what pressure in torr is being exerted on the diver? 0.333 torr 253 torr 760 torr 2.28x10 3 torr 14 A gas occupies 4.00 liters at 751 torr and 37 o C. What is the volume of the gas at 641 torr and 0 o C? 5.32 L 3.01 L 4.13 L 5.32 L
15 A gas occupies 0.850 liters at 1.00 atm and 27 o C. What is the final temperature of the gas when the volume of the gas is 0.650 liters and the pressure 865 torr? -71 o C 174 o C 72 o C -12 o C 16 One mole of an ideal gas at STP occupies 22.4 L. Calculate the volume of one mole of gas at 20 o C and 1.00 atm pressure. 20.9 L 24.0 L 22.4 L 17 Calculate the value of the gas constant in L-atm/mol-deg using the ideal gas law and the fact that one mole of gas occupies 22.41 L at STP (remember that 0.0 o C is 273.1 K. 0.08206 L-atm/mol-deg 6.120x10 3 L-atm/mol-deg 12.19 L-atm/mol-deg 18 How many moles of oxygen gas are in a 3.00 liter vessel filled with oxygen at 750 torr and 25 o C? 92.0 moles 1.44 moles 0.121 moles 19 What is the volume of 0.500 moles of gas at 127 o C and 2.00 atm pressure? 2.61 L 8.21 L 32.8 L 20 14.4 grams of an unknown gas is found to have a volume of 8.00 L at 760 torr and 25 o C. What is the molecular mass of the gas? 44.0 g/mol 0.0579 g/mol 0.0227 g/mol
21 A gas at 750 mm pressure and 27 o C has a density of 2.32 g/l. Which of the following could be the gas? carbon dioxide krypton hydrogen sulfide butane (C 4 H 10 ) 22 Typical popcorn kernels weigh abut 0.13 g, have a volume of 0.095 ml and contain about 0.017 g of water. Use the ideal gas law to calculate the pressure of gaseous water at 100 o C confined to the kernel produced from the conversion of the water to gas. 5.5x10 3 atm 81 atm 3.0x10 2 atm 2.3x10 5 atm 23 Assume the box to the right contains helium (boiling point 4 K) at about 300 K. Which of the boxes below would most closely represent the box if the absolute temperature of the box were approximately halved?
24 In the preceding problem (#23), since the volume of the gas stays constant and the temperature changes, another parameter not included in the figures must change. What is this parameter? The number of moles. The pressure.