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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 33b

State whether each of the following statements is true or false. Justify your answer in each case. (b) HCl is a weak acid.

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Identify the nature of HCl in terms of acid strength. Hydrochloric acid (HCl) is commonly known and used in chemistry.
Recall the definition of a strong acid. A strong acid is one that completely dissociates into its ions in solution.
Consider the dissociation of HCl in water. When HCl is dissolved in water, it dissociates completely into hydrogen ions (H+) and chloride ions (Cl-).
Compare the behavior of HCl with the characteristics of strong acids. Since HCl completely dissociates in solution, it exhibits the key characteristic of a strong acid.
Conclude the classification of HCl based on its dissociation. Given that HCl fully dissociates in water, it should be classified as a strong acid, not a weak acid.

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Key Concepts

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

Acid Strength

Acid strength refers to the ability of an acid to donate protons (H+) in a solution. Strong acids, like hydrochloric acid (HCl), completely dissociate in water, releasing all their protons, while weak acids only partially dissociate. Understanding this distinction is crucial for evaluating the nature of acids.
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Dissociation in Water

Dissociation in water is the process by which an acid separates into its constituent ions when dissolved. For strong acids, this process is complete, leading to a high concentration of H+ ions. In contrast, weak acids result in a dynamic equilibrium between the undissociated acid and its ions, which is essential for determining their strength.
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Percent Dissociation Example

pH Scale

The pH scale measures the acidity or basicity of a solution, with lower values indicating higher acidity. Strong acids typically have low pH values due to their complete dissociation, while weak acids have higher pH values because they do not fully dissociate. This concept helps in understanding the behavior of acids in various chemical contexts.
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