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Ch.17 - Acids and Bases
Tro - Chemistry: A Molecular Approach 5th Edition
Tro5th EditionChemistry: A Molecular ApproachISBN: 9780134874371Not the one you use?Change textbook
All textbooksTro 5th EditionCh.17 - Acids and BasesProblem 99c
Chapter 17, Problem 99c

Determine whether each cation is acidic or pH-neutral. For those cations that are acidic, write an equation that shows how the cation acts as an acid. c. Co3+

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insert step 1: Identify the cation in question, which is \( \text{Co}^{3+} \).
insert step 2: Recognize that \( \text{Co}^{3+} \) is a transition metal cation with a high positive charge, which can lead to acidic behavior.
insert step 3: Understand that highly charged metal cations can polarize water molecules, leading to the release of \( \text{H}^+ \) ions, thus acting as acids.
insert step 4: Write the chemical equation showing \( \text{Co}^{3+} \) acting as an acid: \[ \text{Co}^{3+} + 6 \text{H}_2\text{O} \rightarrow [\text{Co(H}_2\text{O})_6]^{3+} \rightarrow [\text{Co(H}_2\text{O})_5\text{OH}]^{2+} + \text{H}^+ \]
insert step 5: Conclude that \( \text{Co}^{3+} \) is an acidic cation because it can increase the concentration of \( \text{H}^+ \) ions in solution, lowering the pH.

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Key Concepts

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

Acidic Cations

Acidic cations are positively charged ions that can donate protons (H+) in solution, thereby lowering the pH. These cations typically arise from transition metals and can interact with water to form hydronium ions (H3O+). Understanding whether a cation is acidic involves examining its charge and the nature of its interactions with water.
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Hydrolysis of Metal Ions

Hydrolysis refers to the reaction of a metal ion with water, leading to the formation of an acidic solution. When a metal cation like Co3+ is dissolved in water, it can attract water molecules, resulting in the release of protons and the formation of a complex ion. This process is crucial for determining the acidity of the cation in solution.
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pH and Acidity

pH is a measure of the hydrogen ion concentration in a solution, indicating its acidity or basicity. A pH less than 7 signifies an acidic solution, while a pH of 7 is neutral. Understanding the relationship between cations and pH is essential for determining whether a cation is acidic or neutral, as acidic cations will typically lower the pH of the solution.
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Related Practice
Textbook Question

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Textbook Question

Determine whether each cation is acidic or pH-neutral. For those cations that are acidic, write an equation that shows how the cation acts as an acid. a. NH4+