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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 49c

Determine the oxidation number for the indicated element in each of the following substances: c. Mn in KMnO4,

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Identify the oxidation number of potassium (K) in KMnO_4, which is typically +1.
Identify the oxidation number of oxygen (O) in KMnO_4, which is typically -2.
Set up an equation based on the sum of oxidation numbers in the compound KMnO_4, which must equal zero because it is a neutral compound.
Let the oxidation number of manganese (Mn) be x. Write the equation: +1 (for K) + x (for Mn) + 4(-2) (for O) = 0.
Solve the equation for x to find the oxidation number of Mn.

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Key Concepts

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

Oxidation Number

The oxidation number, or oxidation state, is a value assigned to an element in a compound that reflects its degree of oxidation or reduction. It indicates the number of electrons an atom can gain, lose, or share when forming chemical bonds. Oxidation numbers are crucial for understanding redox reactions and determining the electron transfer in chemical processes.
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Rules for Assigning Oxidation Numbers

There are specific rules for assigning oxidation numbers, such as the fact that the oxidation number of an element in its elemental form is zero, and for monoatomic ions, it equals the charge of the ion. In compounds, the sum of the oxidation numbers must equal the overall charge of the compound. These rules help in systematically determining the oxidation state of elements in various compounds.
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Oxidation States in Polyatomic Ions

In polyatomic ions, the oxidation states of the constituent elements must sum to the charge of the ion. For example, in KMnO4, potassium (K) has an oxidation state of +1, and oxygen (O) typically has an oxidation state of -2. By applying these rules, one can deduce the oxidation state of manganese (Mn) in KMnO4, which is essential for understanding its chemical behavior.
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