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Unformatted text preview: Lin (cgl286) Homework 10 Lyon (52370) 1 This print-out should have 33 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. This HW assignment is due Wednesday, April 22, by 11PM. 001 10.0 points To promote ideal behavior of a gas, one should (raise/lower) the pressure and (raise/lower) the temperature of the gas. 1. raise, raise 2. lower, raise correct 3. lower, lower 4. raise, lower Explanation: Low pressure and high temperature both favor ideal behavior. Low pressure helps to ensure that the likelihood of molecules inter- acting with each other is small, thus helping to satisfy one of the assumptions of kinetic molecular theory, namely that gas molecules are not attracted to each other. High temper- ature gives the molecules a greater kinetic en- ergy, helping to ensure that collisions will be as elastic as possible, again helping to satisfy one of the assumptions of kinetic molecular theory. 002 10.0 points In an improved version of the gas law, V is replaced by ( V- nb ). Which of the following would you predict has the largest b ? 1. C 2 H 6 2. C 3 H 8 3. CH 4 4. C 4 H 10 correct 5. C 2 H 4 Explanation: b accounts for the volume being smaller than it actually is because molecules take up space. The larger the molecule, the more it takes up space, so its b will be larger. C 4 H 10 has the biggest MW, so it has the biggest b . 003 10.0 points Rank the following gases in terms of decreas- ing ideality: Cl 2 , H 2 , CO 2 , CH 4 . 1. H 2 > CH 4 > CO 2 > Cl 2 correct 2. CO 2 > CH 4 > H 2 > Cl 2 3. Cl 2 > CH 4 > CO 2 > H 2 4. CH 4 > H 2 > Cl 2 > CO 2 5. CO 2 > Cl 2 > CH 4 > H 2 Explanation: Because all of the gases are non-polar, the only consideration for non-ideality is the size. Larger molecules, evaluated by atomic mass, are less ideal. 004 10.0 points Which of the following molecules would have the largest a and b term, respec- tively, in the van der Waals equation: N 2 , SF 6 , SF 5 Cl , SiH 4 , He . 1. SF 6 and SiH 4 , respectively 2. SF 5 Cl and SF 5 Cl, respectively correct 3. SF 5 Cl and He, respectively 4. N 2 and He, respecitvely 5. SiH 4 and SF 6 , respectively Explanation: SF 5 Cl is the only polar molecule and thus has the largest a term and it is also the largest (in terms of molecular weight) and so has the largest b term as well. 005 10.0 points Lin (cgl286) Homework 10 Lyon (52370) 2 All of the following are gases at room temper- ature and atmospheric pressure. Which one will liquify most easily when pressurized at a certain temperature? 1. H 2 2. F 2 3. NH 3 correct 4. SiH 4 5. Ar Explanation: H 2 , Ar , SiH 4 and F 2 are non-polar. NH 3 is polar and experiences stronger attractive forces, which aid in liquification....
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This note was uploaded on 10/26/2010 for the course CH 52370 taught by Professor Lyon during the Spring '09 term at University of Texas at Austin.
- Spring '09