Study Guide to Liquids & Solids (Intermolecular Forces)

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DISCLAIMER: This Guide is not meant to be exhaustive. That is, I have tried to summarize the essential points of the lectures on this topic. The presence of a topic here does not guarantee a related question on an exam, nor are exam topics limited to what appears in this Guide. As with any Chemistry class, you are responsible for ALL of the assigned readings, problems and lecture material. Lectures will often contain information not covered or given less emphasis in the text.

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Text Reading

Chapter 16, Sections 1 and 2
(pages 764-771)

What should you learn from this section of the course?

This section encompasses two general topics: Liquids and Intermolecular interactions. The latter are not really bonding interactions, but weak forces holding pseudo-molecules together. These interactions include dipole-dipole, hydrogen bonding and induced dipole-induced dipole forces. With only two lectures available, we'll concentrate on a more qualitative approach to intermolecular forces.

General

• Definitions of the non-bonding intermolecular interactions

Intermolecular Interactions

• Understand hydrogen bonding and its implications for molecular structure
• Be able to relate intermolecular forces to physical properties
• Understand the origin of macroscopic observations such as a liquid meniscus

Chapter 16 Problems

Intermolecular forces: 11, 14, 15, 17, 21, 23. Liquids: 29, 33.

Additional Problems

1. Which of the following would be expected to form hydrogen bonds: CH₃Br, (CH₃)₂O and CH₃OH.

2. The compound ClF has a lower boiling point than Cl₂, even though it is polar. Explain.

3. Which of the following would be expected to form intermolecular hydrogen bonds: H₂O₂, CH₃F and H₂SO₄. Draw structures for each hydrogen-bonded molecule.

4. The H-F hydrogen bond energy is greater than the H-O hydrogen bond energy. Solid HF has a lower melting point than ice. Explain.

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