Chemistry 10 Dr. Scholefield Chapter 12 Worksheet Homework is not collected or graded, but should be worked on seriously every week. IMFs, Liquid Properties and Phase Changes 1. What are intermolecular forces (IMFs)? 2. What types of IMFs are found in: Polar covalent substances Nonpolar covalent substances 3. What are the special requirements for hydrogen bonding IMFs to occur in covalent substance? 4. Consider the following covalent compounds, and determine the primary type of IMFs that exist between a collection of its molecules. You will first need to draw the Lewis Structures for these molecules in order to decide whether they are polar or non-polar. CHCl3 CH3NH2 H2O2 SO3 Br2 N2H4 CH2O CS2 PCl3 IBr 5. The substances H2S, O2 and CH3OH have comparable molar masses. Rank the strength of the IMFs that occur in pure samples of each of these substances (1 = strongest, 3 = weakest). 6. Intermolecular forces have a strong influence on the properties of elements and covalent compounds. Consider the following pairs of substances, and determine which substance (1) is more likely to be a gas at RT; (2) is more viscous; (3) is more volatile (4) has the higher boiling point, and (5) has the lower ΔHvap. a. C OO and C SS b. CHHHF and C H H H O H c. NH3 and CH47. The liquid chloroform boils at 61.2 °C (and freezes at –63.5 °C) while the liquid benzene boils at 80.1 °C (and freezes at 5.5 °C). Without knowing (or looking up) the structures of these molecules, use the information provided here to determine which liquid has the stronger IMFs between its molecules. Briefly explain your response. 8. The data below has been collected for Substance X. Use this data to sketch a heat curve for Substance X. Your sketch does not need to be to scale, but it should clearly show relative differences. Normal MP –15 °C ΔHfus 5 kJ/mol csolid < cliquid ≈ cgas Normal BP 130 °C ΔHvap 60
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