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NAME: ______________________________________ AP CHEMISTRY CHAPTER 7 PROBLEM SET #2 (Questions 1-3) Write the letter of the phrase that answers the question or best completes the statement on the line. _____ 1. 1-propanol, CH3CH2CH2CH2OH, boils at 97oC and ethyl methyl ether, CH3CH2OCH3, boils at 7oC, although each compound has an identical chemical composition. The difference that is responsible for the higher boiling temperature is A. molar mass. B. hydrogen bonding. C. density. D. specific heat. E. enthalpy. _____ 2. The Clausius-Clapeyron equation indicates that I. the greater the vapor pressure, the higher the entropy of the vaporization. II. the higher the heat of vaporization, the steeper the slope of lnP vs 1/T. III. the enthalpy of vaporization is equal to the slope of the vapor pressure vs. temperature. A. I only B. II only _____ 3. Which of the following would exist between atoms that had a large difference in electronegativities? A. covalent bonding B. London dispersion forces C. hydrogen bonding D. ionic bonding 4. C. III only D. I and II only E. I, II and III Based upon the following data, determine the ∆Hvap for magnesium and lithium. In which metal is the bonding stronger? Vapor Pressure Temperature (°C) (mm Hg) Li Mg 1. 750. 620. 10. 890. 740. 100. 1080. 900. 400. 1240. 1040. 760. 1310. 1110. 5. The temperature inside a pressure cooker is 115°C. a. Calculate the vapor pressure inside the pressure inside the pressure cooker. At 100.°C, the vapor pressure of water is 1.00 atm. For water, ∆Hvap is 40.7 kJ/mol. b. What would be the temperature inside the pressure cooker if the vapor pressure of water was 3.50 atm? (At 100.°C, the vapor pressure of water is 1.00 atm. For water, ∆Hvap is 40.7 kJ/mol). 6. What pressure would have to be applied to steam at 350.°C to condense the steam to liquid water? 7. The enthalpy of vaporization of acetone is 32.0 kJ/mol. The normal boiling point of acetone is 56.5°C. What is the vapor pressure of acetone at 25.0°C? 8. The complete structural formula of propane, C3H8, and methanoic acid, HCOOH, are shown above. a. In the table below, write the type(s) of intermolecular attractive force(s) that occur in each substance. Substance Propane Methanoic acid b. 9. Boiling Point 229 K 374 K Intermolecular Attractive Force(s) Use principles of intermolecular attractive forces to explain why methanoic acid has a higher boiling point than propane. The vapor pressure of water at 25oC is 23.8 torr; ∆Hvap = 43.9 kJ/mol. a. Determine the vapor pressure of water at 70.oC. b. Determine the percentage error if your experimental results for vapor pressure at 70oC give a result of 225 torr. c. 10. Give structural reasons that support the fact that the boiling temperature of C2H5OH is 78oC and water is 100oC, (both at 760 torr). The following table gives the vapor pressure of hexafluorobenzene as a function of temperature. Temperature (°C) 7.0 27.0 47.0 57.0 67.0 11. Vapor pressure (torr) 32.41 92.47 225.1 334.4 482.9 a. Determine the value of ∆Hvap. b. Use this data to determine the boiling point of the compound. 1-proponal, CH3CH2CH2OH, boils at 97oC and ethyl methyl ether, CH3CH2OCH3 boils at 7oC, although each compound has an identical chemical composition. Explain why 1-propanol has a boiling point so much higher than ethyl methyl ether. 12. Rationalize the difference in boiling points for each of the following pairs of substances: a. n-pentane CH3CH2CH2CH2CH3 36.2oC CH3 neopentane H3C-C-CH3 9.5oC CH3 13. b. n-Pentane n-Propane c. n-Propane dimethyl ether CH3CH2CH2CH2CH3 CH3CH2CH3 CH3CH2CH3 CH3OCH3 36.2oC -42oC -42oC -25oC Predict which of the following substances would have a higher boiling point: Cl2 or I2. JUSTIFY YOUR ANSWER.