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Homework 01 - Version 085 Homework 1 Fakhreddine(53605 This...

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Version 085 – Homework 1 – Fakhreddine – (53605) 1 This print-out should have 14 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 1.0 points On a relative basis, the weaker the intermolec- ular forces in a substance 1. the more it deviates from the ideal gas law. 2. the larger its heat of vaporization. 3. the larger its molar heat capacity as a liquid. 4. the greater its vapor pressure at a partic- ular temperature. correct 5. the higher its melting point. Explanation: Weak intermolecular forces suggest that it is easy to cause molecules of the substance to be pulled away from each other. Thus it will take a relatively low temperature to both melt and boil the substance. Weaker inter- molecular forces also mean that the substance will have a relatively high vapor pressure at a given temperature (which would cause the compound to boil at a lower temperature, since the normal boiling point would occur when the substance’s vapor pressure reaches 760 torr.) 002 1.0 points Which of the following is expected to boil at the highest temperature? 1. CH 4 2. C 4 H 10 3. C 2 H 6 4. C 3 H 8 5. C 5 H 12 correct 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. 003 1.0 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. I and IV only 2. III only 3. I and II only 4. I, III, and IV only correct 5. II 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. 004 1.0 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
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Version 085 – Homework 1 – Fakhreddine – (53605) 2 grams of ice at 0 C to 10 grams of water at 75 C?
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