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HW9 - padilla(tp5647 Homework 9 Sutclie(53770 This...

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padilla (tp5647) – Homework 9 – Sutcliffe – (53770) 1 This print-out should have 25 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A gas has a volume of 2.0 L at a pressure of 3.00 atm. What pressure is needed to change the volume to 6.00 L at constant temperature? 1. 2.0 atm 2. 1.0 atm correct 3. 9.0 atm 4. 4.0 atm Explanation: V 1 = 2.00 L P 1 = 3 atm V 2 = 6.00 L Boyle’s law, P 1 V 1 = P 2 V 2 , relates the vol- ume and pressure of a sample of gas. P 2 = P 1 V 1 V 2 = (3.00 atm) (2.00 L) 6.00 L = 1.0 atm 002 10.0 points At constant temperature if the volume of a gas sample is tripled the pressure will 1. be cut in half. 2. remain the same. 3. be tripled. 4. be one third the original. correct 5. be increased by a factor of 6. Explanation: 3 V 1 = V 2 Boyle’s Law relates the volume and pressure of a sample of gas: P 1 V 1 = P 2 V 2 P 1 V 1 = P 2 (3 V 1 ) P 1 = 3 P 2 P 2 = 1 3 P 1 003 10.0 points A certain quantity of a gas occupies 61.3 mL at 68 C. If the pressure remains constant, what would be the volume of the gas at 128 C? 1. 72 mL correct 2. 92 mL 3. 32 mL 4. 52 mL Explanation: V 1 = 61 . 3 mL T 1 = 68 C = 341 K T 2 = 128 C = 401 K Charles’s law V 1 T 1 = V 2 T 2 relates the volume and absolute (Kelvin) temperature of a sam- ple of gas: V 2 = V 1 T 2 T 1 = (61 . 3mL) (401 K) 341 K = 72 L 004 10.0 points If a sample of gas is heated from 100 C to 300 C at constant pressure, the volume will ? by a factor of ? . 1. increase; about three 2. increase; about 1.5 correct 3. decrease; about 1.5 4. No other answer is correct, because the volume cannot change when the pressure is constant. 5. decrease; about three Explanation: T 1 = 100 C + 273 = 373 K
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padilla (tp5647) – Homework 9 – Sutcliffe – (53770) 2 T 2 = 300 C + 273 = 573 K The temperature increases by a factor of 573 373 = 1 . 5. According to Charles’ Law, the volume of the gas would increase by the same factor. 005 10.0 points A sample of a gas occupies 460 mL at 70.0 C and 1.00 atmosphere. At what temperature would the gas occupy 650 mL at the same pressure? 1. - 30.0 C 2. 435 C 3. 99 C 4. 212 C correct 5. 154 C 6. 188 C 7. 111 C Explanation: V 1 = 460 mL V 2 = 650 mL T 1 = 70.0 C + 273 = 343 K Charles’s law relates the volume and ab- solute (Kelvin) temperature of a sample of gas: V 1 T 1 = V 2 T 2 T 2 = V 2 T 1 V 1 = (650 mL) (343 K) 460 mL = 485 K C = 485 K - 273 = 212 C 006 10.0 points The normal respiratory rate for a human be- ing is 15.0 breaths per minute. The average volume of air for each breath is 505 cm 3 at 20 C and 9 . 95 × 10 4 Pa. What is the volume of air at STP that an individual breathes in one day? Give your answers in cubic meters. 1. 9 . 98 m 3 / day correct 2. 505 cm 3 / day 3. 505 m 3 / day 4. None of these 5. 100 m 3 / day 6. 9 . 95 cm 3 / day Explanation: P 1 = 9 . 95 × 10 4 Pa P 2 = 1 . 01325 × 10 5 Pa T 1 = 20 C + 273 = 293 K V 1 = 505 cm 3 T 2 = 0 C + 273 = 273 K V 2 = ? P 1 V 1 T 1 = P 2 V 2 T 2 V 2 = P 1 V 1 T 2 P 2 T 1 = (9 . 95 × 10 4 Pa)(505 cm 3 )(273 K) (1 . 01325 × 10 5 Pa)(293 K) = 0 . 000462054 m 3 parenleftbigg 15 breaths min parenrightbiggparenleftbigg 60 min hour parenrightbiggparenleftbigg 24 hours day parenrightbigg = 21600 breaths / day parenleftbigg 21600 breaths day parenrightbiggparenleftbigg 0 . 000462054 m 3 breath parenrightbigg = 9 . 98037 m 3 / day 007 10.0 points At STP a gas occupies 121 mL. How many
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