Ch.11 - Liquids & Phase Changes
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- The compound cholesteryl benzoate is a rod-like molecule that undergoes a phase change from the solid to the liq- uid crystal phase at 145.5 °C. When cholesteryl benzoate is mixed with cholesteryl oleyl carbonate, a molecule with a curved shape, the temperature of the solid to liquid crys- tal transition changes. Predict if the transition temperature increases or decreases and explain your reasoning.
Problem 73
- 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?
Problem 75
- Substance X has a vapor pressure of 100 mm Hg at its triple point (48 °C). When 1 mol of X is heated at 1 atm pres- sure with a constant rate of heat input, the following heating curve is obtained: (b) For each of the following, choose which phase of X (solid, liquid, or gas) fits the description. (iii) Has the greatest specific heat
Problem 77
- Which of the following substances would you expect to have a nonzero dipole moment? Explain, and show the direction of each. (a) Cl2O (b) XeF4 (c) Chloroethane, CH3CH2Cl (d) BF3
Problem 78
- Draw three-dimensional structures of PCl3 and PCl5, and then explain why one of the molecules has a dipole moment and one does not.
Problem 81
- Of the two compounds SiF4 and SF4, which is polar and which is nonpolar?
Problem 83
- Fluorine is more electronegative than chlorine, yet fluoromethane 1CH3F; m = 1.86 D2 has a smaller dipole moment than chloromethane 1CH3Cl; m = 1.90 D2. Explain.
Problem 85
- What is the difference between London dispersion forces and dipole–dipole forces?
Problem 86
- Of the substances Xe, CH3Cl, and HF, which has: (a) The smallest dipole–dipole forces?
Problem 89
- For each of the following substances, identify the intermolecular force or forces that predominate. Using your knowledge of the relative strengths of the various forces, rank the substances in order of their normal boiling points: Al2O3, F2, H2O, Br2, ICl, NaCl.
Problem 91
- 1,3-Propanediol can form intramolecular as well as intermolecular hydrogen bonds. Draw a structure of 1,3-propanediol showing an intramolecular hydrogen bond.
Problem 93
- Has the Earth's surface experienced warming as a result of increasing levels of greenhouse gases? If so, by how much?
Problem 132
- Propanol (PrOH) and methyl methacrylate (MMA) asso-ciate in solution by an intermolecular force, forming an adduct represented as PrOH•MMA. The equilibrium con- stant for the association reaction is Kc = 0.701 at 298 K. (b) Draw a plausible structure for the PrOH • MMA adduct. Use to signify an intermolecular interaction.
Problem 163