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Ch.11 - Liquids and Intermolecular Forces
All textbooksBrown 14th EditionCh.11 - Liquids and Intermolecular ForcesProblem 78a
Chapter 11, Problem 78a

The table below shows the normal boiling points of benzene and benzene derivatives.
(a) How many of these compounds exhibit dispersion interactions?

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1
Step 1: Understand that dispersion forces, also known as London dispersion forces or van der Waals forces, are a type of intermolecular force that exist between all molecules, regardless of whether they are polar or nonpolar. These forces are caused by temporary fluctuations in electron distribution within molecules, which create temporary positive and negative charges that attract other molecules.
Step 2: Recognize that all molecules, including benzene and its derivatives, exhibit dispersion interactions. This is because all molecules have electrons that can create temporary charge imbalances.
Step 3: Look at the table of benzene and benzene derivatives. Count the number of compounds listed.
Step 4: Since all compounds exhibit dispersion interactions, the number of compounds that exhibit these interactions is equal to the total number of compounds listed in the table.
Step 5: Therefore, to answer the question, count the total number of compounds in the table. This is the number of compounds that exhibit dispersion interactions.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Dispersion Interactions

Dispersion interactions, also known as London dispersion forces, are weak intermolecular forces that arise from temporary fluctuations in electron density within molecules. These fluctuations create instantaneous dipoles that induce dipoles in neighboring molecules, leading to an attractive force. All molecules, regardless of polarity, exhibit dispersion interactions, but they are particularly significant in nonpolar compounds.
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Boiling Point and Intermolecular Forces

The boiling point of a substance is the temperature at which its vapor pressure equals the external pressure, allowing it to transition from liquid to gas. Intermolecular forces, including dispersion interactions, hydrogen bonding, and dipole-dipole interactions, play a crucial role in determining boiling points. Stronger intermolecular forces typically result in higher boiling points, as more energy is required to overcome these attractions.
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Benzene and Its Derivatives

Benzene is an aromatic hydrocarbon with a stable ring structure, characterized by its delocalized π electrons. Its derivatives are compounds that contain the benzene ring but may have different functional groups attached. The presence of these functional groups can influence the types and strengths of intermolecular forces present, including dispersion interactions, which are relevant for understanding their boiling points.
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Related Practice
Textbook Question

Suppose you have two colorless molecular liquids, one boiling at - 84 °C, the other at 34 °C, and both at atmospheric 6 pressure. Which of the following statements is correct? For each statement that is not correct, modify the statement so that it is correct. (d) The two liquids have identical vapor pressures at their normal boiling points.

Textbook Question

Suppose you have two colorless molecular liquids, one boiling at - 84 °C, the other at 34 °C, and both at atmospheric 6 pressure. Which of the following statements is correct? For each statement that is not correct, modify the statement so that it is correct. (e) At - 84 °C both liquids have vapor pressures of 760 mm Hg.

Textbook Question

Two isomers of the planar compound 1,2-dichloroethylene are shown here.

(a) Which of the two isomers will have the stronger dipole– dipole forces?

Textbook Question

The table below shows the normal boiling points of benzene and benzene derivatives. (e) Why is the boiling point of phenol the highest of all?

Textbook Question

Use the normal boiling points propane (C3H8) -42.1 °C butane (C4H10) -0.5 °C pentane (C5H12) 36.1 °C hexane (C6H14) 68.7 °C heptane (C7H16) 98.4 °C to estimate the normal boiling point of octane (C8H18). Explain the trend in the boiling points.