4.7 worksheet answers

SCH 4U1 4.7 Intermolecular Forces – Worksheet - ANSWERS 1. Draw the following substances. Then, identify all the intermolecular forces present in pure samples of the following substances: a) SO 2 london dispersion, dipole dipole b) H 2 O london dispersion, dipole dipole, hydrogen bonding c) CH 2 Cl 2 london dispersion, dipole dipole d) SCO london dispersion, dipole dipole e) PCl 3 london dispersion, dipole dipole f) XeF 4 london dispersion 2. Based on the intermolecular forces present, predict the relative boiling points of each of the substances below. Arrange each series of substances in order of increasing boiling point. State your reasons for the order you use (identify the forces and explain how they affect the boiling point). a. methoxymethane (CH 3 OCH 3 ), ethanol (CH 3 CH 2 OH), and propane (CH 3 CH 2 CH 3 ) lowest bp: propane (CH 3 CH 2 CH 3 ) < methoxymethane (CH 3 OCH 3 )< ethanol (CH 3 CH 2 OH) highest bp Dimethyl ether cannot form hydrogen bonds (no O-H bond), but is polar and has dipole-dipole forces. Ethanol can form hydrogen bonds. propane is nonpolar, so it has only London dispersion forces. The boiling point increases as the strength of the intermolecular forces increase: London dispersion < dipole-dipole forces < hydrogen bonds [All have similar molar masses: 46.07g/mol, 46.07g/mol and 44.09g/mol respectively.] b. Br 2 , Cl 2 , I 2 lowest bp: Cl 2 < Br 2 < I 2 highest bp All are nonpolar molecules so only London dispersion forces are present. London dispersion forces get stronger as molar mass increases. 3. Rank the following substances in terms of increasing boiling points: water, CH2O, methane, CO2 methane, CO 2 , CH 2 O, water 4. Rank the following compounds from lowest to highest boiling point: calcium carbonate, methane, methanol (CH4O), dimethyl ether (CH 3 OCH 3 ). By using intermolecular forces, we can tell that these compounds will rank: methane (Van der Waals forces), dimethyl ether (dipole-dipole forces), methanol (hydrogen bonding), calcium carbonate (ionic bonds that are much stronger than any of the 3 intermolecular forces). 5. Compare the solubility of each of the following pairs of compounds in water. Which compound if any, would be soluble? Explain why.