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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 111f

Assign oxidation numbers to each element in the following ions. (f) V2O7 4-

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Step 1: Recall the rules for assigning oxidation numbers. Oxygen typically has an oxidation number of -2.
Step 2: Let the oxidation number of vanadium (V) be x.
Step 3: Write the equation for the sum of oxidation numbers in the ion: 2x + 7(-2) = -4.
Step 4: Simplify the equation: 2x - 14 = -4.
Step 5: Solve for x to find the oxidation number of vanadium.

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Key Concepts

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

Oxidation Numbers

Oxidation numbers are assigned to elements in a compound to indicate the degree of oxidation or reduction of each element. They are useful for understanding electron transfer in redox reactions. The rules for assigning oxidation numbers include that the oxidation number of an element in its elemental form is zero, and for monoatomic ions, it equals the charge of the ion.
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Rules for Assigning Oxidation Numbers

There are specific rules for assigning oxidation numbers, such as oxygen typically having an oxidation number of -2, and hydrogen usually being +1. In polyatomic ions, the sum of the oxidation numbers must equal the overall charge of the ion. For example, in the ion V2O7 4-, the total oxidation number must equal -4.
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Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms that are covalently bonded and carry a net charge. Understanding the structure and charge of polyatomic ions is essential for assigning oxidation numbers correctly. In the case of V2O7 4-, the vanadium and oxygen atoms must be analyzed together to determine their respective oxidation states.
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