13. Liquids, Solids & Intermolecular Forces

What is the vapor pressure of SiCl4 in mm Hg at 30.0 °C? (See Problem 11.27.)

Dichloromethane, CH2Cl2, is an organic solvent used for removing caffeine from coffee beans. The following table gives the vapor pressure of dichloromethane at various tem- peratures. Fill in the rest of the table, and use the data to plot curves of Pvap versus T and ln Pvap versus 1/T.

Choose any two temperatures and corresponding vapor pressures in the table given in Problem 11.30, and use those values to calculate ΔHvap for dichloromethane in kJ/mol. How does the value you calculated compare to the value you read from your plot in Problem 11.32?

Dichlorodifluoromethane, CCl2F2, one of the chlorofluo- rocarbon refrigerants responsible for destroying part of the Earth's ozone layer, has Pvap = 40.0 mm Hg at -81.6 °C and Pvap = 400 mm Hg at -43.9 °C. What is the normal boiling point of CCl2F2 in °C?

This table displays the vapor pressure of ammonia at several different temperatures. Use the data to determine the heat of vaporization and normal boiling point of ammonia. Temperature (K) Pressure (torr) 200 65.3 210 134.3 220 255.7 230 456.0 235 597.0

Ethanol has a heat of vaporization of 38.56 kJ>mol and a normal boiling point of 78.4 °C. What is the vapor pressure of ethanol at 15 °C?

Benzene has a heat of vaporization of 30.72 kJ/mol and a normal boiling point of 80.1 °C. At what temperature does benzene boil when the external pressure is 445 torr?

Carbon disulfide has a vapor pressure of 363 torr at 25 °C and a normal boiling point of 46.3 °C. Find ΔHvap for carbon disulfide.

The chlorofluorocarbon refrigerant trichlorofluoromethane, CCl3F, has Pvap = 100.0 mm Hg at -23 °C and ΔHvap = 24.77 kJ>mol. (b) What is ΔSvap for trichlorofluoromethane?

The following table gives the vapor pressure of hexafluorobenzene (C6F6) as a function of temperature: (a) By plotting these data in a suitable fashion, determine whether the Clausius–Clapeyron equation (Equation 11.1) is obeyed. If it is obeyed, use your plot to determine ∆Hvap for C6F6.

Supposethevaporpressureofasubstanceismeasuredattwo different temperatures. (a) By using the Clausius–Clapeyron equation (Equation 11.1) derive the following relationship between the vapor pressures, P1 and P2, and the absolute tem- peratures at which they were measured, T1 and T2: (b) Gasoline is a mixture of hydrocarbons, a component of which is octane (CH3CH2CH2CH2CH2CH2CH2CH3). Octane has a vapor pressure of 13.95 torr at 25 °C and a vapor pressure of 144.78 torr at 75 °C. Use these data and the equa- tion in part (a) to calculate the heat of vaporization of octane. (c) By using the equation in part (a) and the data given in part (b), calculate the normal boiling point of octane. Compare your answer to the one you obtained from Exercise 11.81. (d) Calculate the vapor pressure of octane at - 30 °C.

The following data present the temperatures at which certain vapor pressures are achieved for dichloromethane (CH2Cl2) and methyl iodide (CH3I): (c) The order of volatility of these two substances changes as the temperature is increased. What quantity must be different for the two substances for this phenom- enon to occur?

The vapor pressure of ethanol (C2H5OH) at 19 °C is 40.0 torr. A 1.00-g sample of ethanol is placed in a 2.00 L con- tainer at 19 °C. If the container is closed and the ethanol is allowed to reach equilibrium with its vapor, how many grams of liquid ethanol remain?