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Chapter 10 Worked Example 1. Explain the trend in the boiling points of the hydrogen halides: HCl, -85 o C; HBr, -67 o C; HI, -35 o C. - Electronegativity differences: HCl > HBr > HI. - Number of electrons and London forces: HCl < HBr < HI.
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Chapter 10 Worked Example 1 Explain the trend in the boiling points of the hydrogen halides: HCl, -85 oC; HBr, -67 oC; HI, -35 oC. - Electronegativity differences: HCl > HBr > HI - Number of electrons and London forces: HCl < HBr < HI → not by dipole-dipole forces, but by London forces
Chapter 10 Worked Example 4 Identify the kinds of intermolecular forces that might arise between molecules of each of the following substances: (a) NH2OH; (b) CBr4; (c) H2SeO4; (d) SO2 • Solution • London forces, dipole-dipole forces, hydrogen bonding • London forces • London forces, dipole-dipole forces, hydrogen bonding • London forces, dipole-dipole forces
Chapter 10 Worked Example 5 Suggest, giving reasons, which substance in each of the following pairs is likely to have the higher normal melting point (Lewis structures may help your arguments): • HCl or NaCl; (b) C2H5OC2H5 (diethyl ether) or C4H9OH (butanol); • (c) CHI3 or CHF3; (d) C2H4 or CH3OH. Solution
Chapter 10 Worked Example 7 Predict how each of the following properties of a liquid varies as the strength of intermolecular forces increases and explain your reasoning: (a) boiling point; (b) viscosity; (c) surface tension. Solution