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Unformatted text preview: muir (cem2577) H02: Chapter 16 McCord (52405) 1 This print-out should have 16 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. Note that some of these problems WILL require you to remember (review) your trends in intermolecular forces discussed in CH301 and at the beginning of Chapter 16. 001 10.0 points Which of the following is expected to boil at the highest temperature? 1. C 3 H 8 2. C 4 H 10 3. C 5 H 12 correct 4. CH 4 5. C 2 H 6 Explanation: The boiling point tends to increase with increasing molecular weight. C 5 H 12 has the biggest MW, so it should boil at the highest temperature. 002 10.0 points Consider the following statements: I) The vapor pressure of ethyl alcohol in- creases as temperature increases. II) Liquids with low molecular weight ex- hibit relatively high vapor pressures, liq- uids with high molecular weight show relatively low vapor pressures, and solids do not have vapor pressures. III) A liquid boils at a higher temperature at sea level than on top of a mountain. IV) The temperature of boiling water inside a pressure cooker at sea level is above 100 C. Which response contains all of the TRUE statements, and no others? 1. III only 2. II and IV only 3. I, III, and IV only correct 4. I and II only 5. I and IV only Explanation: Solids can have vapor pressures. CO 2 sub- limes (s g) and therefore has a vapor pres- sure. When temperature increases, molecules have greater energy to overcome intermolec- ular forces/bonds and will therefore have in- creased vapor pressures. Atmospheric pressure is greater at sea level. Molecules require more energy (higher tem- peratures) to vaporize when pressure is high. 003 10.0 points The specific heat of water is 1 . 00 cal / g C, the heat of vaporization of water is 540 cal/g, and the heat of fusion of water is 80 cal/g. How much heat would be required to convert 10 grams of ice at 0 C to 10 grams of water at 75 C? 1. 6150 cal 2. 15.5 cal 3. 155 cal 4. 1.55 kcal correct 5. 61.5 kcal Explanation: 10 g H 2 O(s) C step 1- 10 g H 2 O( ) C step 2- 10 g H 2 O( ) 75 C Step 1: 80 cal g (10 g) = 800 cal Step 2: 1 cal g C (10 g)(75- 0) C = 750 cal Total = 800 cal + 750 cal = 1550 cal = 1 . 55 kcal 004 10.0 points It is found that 600 J of heat are required to muir (cem2577) H02: Chapter 16 McCord (52405) 2 melt 15 g of a compound. What is the heat of fusion of this compound? 1. (600) (15) J/g 2. (600) (1000) 15 kJ/g 3. This cannot be answered without knowing the specific heat of the solid substance....
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This note was uploaded on 02/03/2009 for the course CH 52405 taught by Professor Mccord during the Spring '09 term at University of Texas at Austin.
- Spring '09