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Ch.21 - Transition Elements and Coordination Chemistry
Chapter 21, Problem 6

Arrange the following substances in order of increasing strength as oxidizing agents, and account for the trend: (a) Mn2+ (b) MnO2 (c) MnO4-.

Verified step by step guidance
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Step 1: Understand the concept of oxidizing agents. An oxidizing agent is a substance that gains electrons in a chemical reaction and is reduced in the process. The strength of an oxidizing agent is determined by its ability to accept electrons.
Step 2: Consider the oxidation states of manganese in each species. Mn2+ has an oxidation state of +2, MnO2 has an oxidation state of +4, and MnO4- has an oxidation state of +7.
Step 3: Recognize that the higher the oxidation state, the stronger the oxidizing agent, because it has a greater tendency to gain electrons and be reduced to a lower oxidation state.
Step 4: Arrange the substances based on their oxidation states. MnO4- with the highest oxidation state of +7 is the strongest oxidizing agent, followed by MnO2 with +4, and Mn2+ with +2 being the weakest.
Step 5: Account for the trend by explaining that MnO4- is the strongest oxidizing agent because it can gain the most electrons to reach a stable oxidation state, while Mn2+ is already in a relatively stable state and has less tendency to gain electrons.

Key Concepts

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

Oxidizing Agents

An oxidizing agent is a substance that gains electrons in a chemical reaction, causing another substance to be oxidized. The strength of an oxidizing agent is determined by its ability to accept electrons. Stronger oxidizing agents have a greater tendency to undergo reduction, which is often influenced by their oxidation states and the stability of the resulting species.
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Oxidation States of Manganese

Manganese can exist in multiple oxidation states, ranging from -3 to +7. The oxidation state of manganese in a compound affects its ability to act as an oxidizing agent. Generally, higher oxidation states correspond to stronger oxidizing properties, as these species are more eager to gain electrons to achieve a lower, more stable oxidation state.
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Trends in Oxidizing Strength

The trend in oxidizing strength can be analyzed by comparing the oxidation states and the stability of the manganese species. For example, MnO4- (with Mn in the +7 state) is a strong oxidizing agent due to its high oxidation state, while Mn2+ (with Mn in the +2 state) is a weaker oxidizing agent. MnO2, with Mn in the +4 state, falls in between, illustrating how oxidation state influences oxidizing strength.
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