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Ch.20 - Electrochemistry
Chapter 20, Problem 91a

Determine whether or not each metal, if coated onto iron, would prevent the corrosion of iron. a. Zn

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1
Step 1: Understand the concept of corrosion. Corrosion is a natural process that converts a refined metal into a more chemically stable form such as its oxide, hydroxide, or sulfide. In the case of iron, it is the process of iron oxidizing to form iron(III) oxide, commonly known as rust.
Step 2: Understand the concept of sacrificial protection. This is a method of corrosion protection where a more reactive metal (sacrificial metal) is used to protect a less reactive metal. The more reactive metal will corrode first, protecting the less reactive metal from corrosion.
Step 3: Look at the reactivity series of metals. The reactivity series is a list of metals arranged in order of their decreasing reactivity. In the reactivity series, Zinc (Zn) is above Iron (Fe), meaning Zinc is more reactive than Iron.
Step 4: Apply the concept of sacrificial protection. Since Zinc is more reactive than Iron, if Zinc is coated onto Iron, it will corrode first, thereby protecting the Iron from corrosion.
Step 5: Conclude the problem. Therefore, Zinc, if coated onto iron, would prevent the corrosion of iron.

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Key Concepts

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

Galvanic Protection

Galvanic protection is a method of preventing corrosion by using a more reactive metal to protect a less reactive one. When a more reactive metal, such as zinc, is coated onto iron, it acts as a sacrificial anode. This means that zinc will corrode preferentially, thereby protecting the underlying iron from oxidation and rusting.
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Electrochemical Series

The electrochemical series is a list of metals arranged by their standard electrode potentials. Metals higher in the series are more reactive and can displace those lower in the series from their compounds. Understanding where zinc and iron fall in this series helps predict that zinc can effectively protect iron from corrosion due to its higher reactivity.
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Corrosion Mechanism

Corrosion is an electrochemical process where metals react with environmental factors, leading to deterioration. For iron, corrosion typically occurs when it oxidizes in the presence of moisture and oxygen, forming rust. By applying a protective coating of a more reactive metal like zinc, the corrosion mechanism can be interrupted, thus extending the life of the iron.
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