solids,+heat+transfer+and+phase+diagram

solids,+heat+transfer+and+phase+diagram - Principles of...

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Intermolecular Forces of Attraction Principles of General Chemistry, 2 nd ed. By M. Silberberg Chemistry, 8th ed. by W. Whitten, R. Davis, R., M. L. Peck, and G. Stanley. Exercise For each pair of substances, identify the key intermolecular force(s) in each substance, and select the substance with the higher boiling point: (a) MgCl 2 or PCl 3 (b) CH 3 NH 2 or CH 3 F (c) CH 3 OH or CH 3 CH 2 OH (d) Hexane (CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 ) or 2,2-dimethylbutane CH 3 CCH 2 CH 3 CH 3 CH 3 Answer (a) Mg 2+ and Cl - are held together by ionic bonds while PCl 3 is covalently bonded and the molecules are polar and held together by dipole-dipole interactions. Ionic interactions are stronger than dipole interactions and so MgCl 2 has the higher boiling point. (b) CH 3 NH 2 and CH 3 F are both covalent compounds and have bonds which are polar. CH 3 NH 2 can H bond while that in CH 3 F cannot. Therefore, CH 3 NH 2 has the stronger interactions and the higher boiling point. Answer (c) Both CH 3 OH and CH 3 CH 2 OH can H bond but CH 3 CH 2 OH has more CH for more dispersion force interaction and higher molecular weight. Therefore, CH 3 CH 2 OH has the higher boiling point. (d) Hexane and 2,2-dimethylbutane are both nonpolar with only dispersion forces to hold the molecules together. Hexane has the larger surface area and therefore, the greater dispersion forces and higher boiling point. Answer Molecules that has the larger surface area b has the greater dispersion forces b has higher boiling point. Principles of General Chemistry, 2 nd ed. By M. Silberberg Chemistry, 8th ed. by W. Whitten, R. Davis, R., M. L. Peck, and G. Stanley. The Condensed Phases: Solids and Liquids
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7 • Amorphous solids do not have a well ordered molecular structure. – Examples include waxes, glasses, asphalt. • Crystalline solids have well defined structures that
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solids,+heat+transfer+and+phase+diagram - Principles of...

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