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Ch.16 - Acid-Base Equilibria
Chapter 16, Problem 99

Indicate whether each of the following statements is correct or incorrect. (e) The percent ionization of a weak acid in water increases as the concentration of the acid decreases.

Verified step by step guidance
1
Understand the concept of percent ionization: Percent ionization refers to the fraction of acid molecules that dissociate into ions in solution, expressed as a percentage.
Recall the behavior of weak acids: Weak acids do not completely dissociate in water. The degree of ionization depends on the acid's strength and concentration.
Consider the effect of concentration on ionization: As the concentration of a weak acid decreases, the equilibrium shifts to favor more ionization according to Le Chatelier's principle.
Apply Le Chatelier's principle: When the concentration of the acid decreases, the system compensates by increasing the ionization to maintain equilibrium, thus increasing the percent ionization.
Conclude the statement's correctness: Based on the principles of equilibrium and ionization, the statement that the percent ionization of a weak acid increases as the concentration decreases is correct.

Key Concepts

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

Weak Acids and Ionization

Weak acids are substances that partially dissociate in water to produce hydrogen ions (H+) and their conjugate base. The degree of ionization is a measure of how much of the acid has dissociated into ions. Unlike strong acids, which fully dissociate, weak acids establish an equilibrium between the undissociated acid and the ions produced.
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Calculating Percent Ionization of Weak Acids

Percent Ionization

Percent ionization is defined as the ratio of the concentration of ionized acid to the initial concentration of the acid, multiplied by 100. It provides a way to express the strength of a weak acid in terms of how much of it has dissociated into ions. This value can change with varying concentrations of the acid.
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Percent Ionization Example

Effect of Concentration on Ionization

For weak acids, as the concentration of the acid decreases, the percent ionization increases. This occurs because a lower concentration leads to a smaller amount of undissociated acid, allowing a greater proportion of the acid to ionize. This relationship is a key characteristic of weak acid behavior in solution.
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