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11 Intermolecular Forces Solutions to Exercises (b) Both gases are influenced by London dispersion forces. The heavier the gas particles, the stronger the London dispersion forces. The heavier Xe is a liquid at the specified conditions, while the lighter Ar is a gas. (c) Both gases are influenced by London dispersion forces. The larger, diatomic molecules are more polarizable, experience stronger dispersion forces, and have the higher boiling point. (d) Acetone and 2-methylpropane are molecules with similar molar masses and London dispersion forces. Acetone also experiences dipole-dipole forces and has the higher boiling point. 11.19 (a) Polarizability is the ease with which the charge distribution (electron cloud) in a molecule can be distorted to produce an instantaneous dipole. (b) Sb is most polarizable because its valence electrons are farthest from the nucleus and least tightly held. (c) Polarizability increases as molecular size (and thus molecular weight) increases. In order of increasing polarizability: CH₄