Iron corrodes to produce rust, Fe₂O₃, but other corrosion products that can form are Fe(O)(OH), iron oxyhydroxide, and magnetite, Fe₃O₄. (a) What is the oxidation number of Fe in iron oxyhydroxide, assuming oxygen's oxidation number is -2? (b) The oxidation number for Fe in magnetite was controversial for a long time. If we assume that oxygen’s oxidation number is - 2, and Fe has a unique oxidation number, what is the oxidation number for Fe in magnetite? (O)(OH), iron oxyhydroxide, and magnetite, Fe₃O₄. (c) It turns out that there are two different kinds of Fe in magnetite that have different oxidation numbers. Suggest what these oxidation numbers are and what their relative stoichiometry must be, assuming oxygen’s oxidation number is -2.

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Determine the general formula for iron oxyhydroxide, which is Fe(O)(OH).

Assign oxidation numbers to the known elements: Oxygen (O) typically has an oxidation number of -2, and Hydrogen (H) has an oxidation number of +1.

Set up an equation to solve for the oxidation number of iron (Fe). Let x be the oxidation number of Fe.

The sum of the oxidation numbers in a neutral compound must equal zero. Therefore, the equation is: x + (-2) + (+1) = 0.

Solve the equation for x to find the oxidation number of Fe.

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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. In compounds, the oxidation number helps in determining how electrons are distributed among atoms, which is crucial for understanding redox reactions.

Rules for Assigning Oxidation Numbers

There are specific rules for assigning oxidation numbers, including that the oxidation number of oxygen is typically -2 in compounds, and the sum of oxidation numbers in a neutral compound must equal zero. For example, in iron oxyhydroxide, the oxidation numbers of all elements must be calculated to ensure they balance to zero, which is essential for determining the oxidation state of iron.

Iron Oxyhydroxide Structure

Iron oxyhydroxide is a compound that contains iron, oxygen, and hydroxide ions. Its general formula can be represented as Fe(O)(OH), where the presence of hydroxide (OH) groups influences the oxidation state of iron. Understanding the structure of this compound is important for calculating the oxidation number of iron, as it directly relates to how iron interacts with oxygen and hydroxide in the compound.