Victory for the ACT Student Text 15e

348 • S CIENCE

Passage V A series of three experiments was designed to investigate the interrelationships „‡–™‡‡ ˜ƒ”‹‘—• ˆƒ…–‘”• ‘™ –‘ ‹ϐŽ—‡…‡ gases: temperature (kelvin, K), pressure (atmospheres, atm), volume (liters, L), and the number of moles of gas. Experi ent 1 •ƒ’Ž‡ ‘ˆ ‰ƒ• ™‹–Š ƒ ϐ‹š‡† —„‡” ‘ˆ moles is at 200 K and a volume of 0.30 L was found to have a pressure of 0.40 atm. After the temperature was raised to 400 K while keeping the volume the same, the pressure was found to be 0.80 atm. Experiment 2 •ƒ’Ž‡ ‘ˆ ‰ƒ• ™‹–Š ƒ ϐ‹š‡† —„‡” ‘ˆ moles is at 200 K had a pressure of 0.50 atm when its volume was 1 L. Its volume was then increased to 2 L at constant temperature. The resulting pressure was 0.25 atm. Experiment 3 Two moles of a gas were found to occupy 44.8 L at 1 atm and 273 K. Four moles of the same gas are added to the system with temperature and pressure held constant, resulting in a new volume of 89.6 L. 28. Which of the following hypotheses is (are) supported by the results of Experiment 1? I. The pressure of the gas is proportional to its volume at constant temperature. II. The volume of the gas is proportional to its temperature at constant pressure. III. The pressure of the gas is proportional to its temperature at constant volume. F. I only G. I and II only H. III only J. II and III only 29. The results of Experiment 2 support the hypothesis that if the temperature of a gas is held constant, then the pressure: A. increases as the volume increases. B. decreases as the volume increases. C. does not depend strongly on the volume. D. Cannot be determined from the given

30. The result of Experiment 3 supports the hypothesis that if both the pressure and the temperature of a gas are held constant, then the volume: F. varies inversely with the number of moles of gas. G. varies directly with the number of moles of gas. H. is raised to a maximum value of 134.4 L when additional gas is added. J. does not depend on the number of moles of gas. 31. An experimenter put 0.08 moles of gas ‹–‘ ƒ Ͷ ϐŽƒ• ƒ– ʹ͹͵ ƒ† ͲǤͶͶͺ ƒ–Ǥ She allowed 0.02 moles of the gas to escape, and she put the remaining gas ‹–‘ ƒ •ƒŽŽ‡” ϐŽƒ• –Šƒ–…ƒ—•‡† –Š‡ pressure to remain at 0.448 atm, while the temperature was kept constant as well. According to Experiment 3, the ˜‘Ž—‡ ‘ˆ –Š‡ •ƒŽŽ‡” ϐŽƒ• —•– „‡ǣ A. 0.06 L. B. 2 L. C. 3 L. D. 5 L. 32. In an additional experiment, 0.06 moles of a gas originally at 0.1 atm and 273 K occupy a volume of 13.4 L. The temperature is then changed to 300 K and the volume is changed to 10.0 L. To predict –Š‡ ϐ‹ƒŽ ’”‡••—”‡ ‘ –Š‡ ͲǤͲ͸ ‘Ž‡• ‘ˆ ‰ƒ•ǡ a student should use the results of: I. Experiment 1. II. Experiment 2. III. Experiment 3. F. I only G. II only H. I and II only J. I and III only 33. Š‡ ϐ‹ƒŽ ’”‡••—”‡ ‘ˆ –Š‡ ‰ƒ• †‡•…”‹„‡† ‹ the previous question will be: A. less than 0.1 atm. B. equal to 0.1 atm. C. greater than 0.1 atm. D. Cannot be determined from the given information

Throwback to Science You are not required to know ƒ› •’‡…‹ϐ‹… chemical formulas for the ACT, but any question dealing with the volume, temperature, and pressure of a gas it is helpful to remember the ideal gas law: PV = nRT , where P = pressure (in atm), V = volume (in liters), n = moles, R = universal gas constant (.08206 L atm mol –1 K –1 ), and T = temperature (in Kelvin).