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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 117

Tell for each of the following substances whether the oxidation number increases or decreases in a redox reaction. (a) An oxidizing agent (b) A reducing agent (c) A substance undergoing oxidation (d) A substance undergoing reduction

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Identify the role of an oxidizing agent in a redox reaction: it gains electrons and causes another substance to be oxidized.
Determine the change in oxidation number for an oxidizing agent: it decreases as it gains electrons.
Identify the role of a reducing agent in a redox reaction: it loses electrons and causes another substance to be reduced.
Determine the change in oxidation number for a reducing agent: it increases as it loses electrons.
Understand the process of oxidation and reduction: a substance undergoing oxidation increases its oxidation number, while a substance undergoing reduction decreases its oxidation number.

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Key Concepts

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

Oxidation and Reduction

Oxidation and reduction are chemical processes that involve the transfer of electrons between substances. Oxidation refers to the loss of electrons, resulting in an increase in oxidation number, while reduction involves the gain of electrons, leading to a decrease in oxidation number. These processes are always coupled, meaning that when one substance is oxidized, another is reduced.
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Oxidizing and Reducing Agents

An oxidizing agent is a substance that facilitates oxidation by accepting electrons from another substance, thereby causing the oxidation number of that substance to increase. Conversely, a reducing agent donates electrons to another substance, leading to a decrease in its oxidation number. Understanding the roles of these agents is crucial for identifying changes in oxidation states during redox reactions.
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Oxidation Numbers

Oxidation numbers are assigned to atoms in a compound to indicate their degree of oxidation or reduction. They help track electron transfer in redox reactions. An increase in oxidation number signifies oxidation, while a decrease indicates reduction. By analyzing the oxidation numbers of reactants and products, one can determine the changes occurring during the reaction.
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