Problem 12 - General Chemistry

Question

Give an example of a displacement reaction. What is the oxidizing agent? What is the reducing agent?

Step-by-Step Solution

Answer

Example: \( \text{Zn} + \text{CuSO}_4 \rightarrow \text{ZnSO}_4 + \text{Cu} \). Oxidizing agent: \( \text{CuSO}_4 \). Reducing agent: \( \text{Zn} \).

Step 1: Understanding Displacement Reactions

A displacement reaction occurs when one element is displaced from a compound by another element. Typically, this involves an element reacting with a compound, leading to the "exchange" of elements.

Step 2: Selecting a Reaction Example

Let's consider the reaction between zinc metal and copper(II) sulfate solution: \[ \text{Zn} + \text{CuSO}_4 \rightarrow \text{ZnSO}_4 + \text{Cu} \]. Here, zinc displaces copper from copper sulfate.

Step 3: Identify the Oxidizing Agent

The oxidizing agent is the substance that gains electrons. In the reaction \( \text{Zn} + \text{CuSO}_4 \rightarrow \text{ZnSO}_4 + \text{Cu} \), copper(II) ions (\( \text{Cu}^{2+} \)) gain two electrons to become copper metal (\( \text{Cu} \)), so \( \text{CuSO}_4 \) is the oxidizing agent.

Step 4: Identify the Reducing Agent

The reducing agent is the substance that loses electrons. In the same reaction, zinc metal (\( \text{Zn} \)) loses two electrons to become zinc ions (\( \text{Zn}^{2+} \)), making \( \text{Zn} \) the reducing agent.

Key Concepts

Oxidizing Agent

An oxidizing agent is a critical component in many chemical reactions, particularly redox reactions where the transfer of electrons takes place. It is essentially the substance that gains electrons during the reaction. By accepting electrons, an oxidizing agent facilitates the oxidation of another substance. This means it removes electrons from that substance, leading to its increase in oxidation state. In the context of the zinc and copper sulfate reaction, the copper(II) sulfate (\( \text{CuSO}_4 \)) acts as the oxidizing agent. Here, the copper ions (\( \text{Cu}^{2+} \)) gain two electrons provided by zinc to become copper metal (\( \text{Cu} \)). It's crucial to remember that while the oxidizing agent itself is reduced, it plays a pivotal role in driving the reaction forward.

Reducing Agent

The concept of a reducing agent is closely linked to that of an oxidizing agent, as they work in tandem during a redox reaction. A reducing agent is the substance that donates electrons to another substance, triggering the latter's reduction. Therefore, the reducing agent itself becomes oxidized as it loses electrons. In the displacement reaction involving zinc metal and copper(II) sulfate solution, zinc (\( \text{Zn} \)) serves as the reducing agent. As zinc provides two electrons to the copper ions, it changes from neutral zinc atoms to zinc ions (\( \text{Zn}^{2+} \)). This electron loss signifies oxidation for zinc, highlighting its role as the reducing agent in facilitating the reduction of the copper ions.

Zinc and Copper Sulfate Reaction

The reaction between zinc and copper(II) sulfate is a classic example of a displacement, or single replacement, reaction. In this specific reaction:

• Zinc metal (\( \text{Zn} \)) reacts with copper(II) sulfate (\( \text{CuSO}_4 \)).
• The end products are zinc sulfate (\( \text{ZnSO}_4 \)) and copper metal (\( \text{Cu} \)).

This format of reaction is particularly instructive for understanding electron transfer. Zinc, being more reactive, displaces copper from copper(II) sulfate. Such reactions are fundamental to many industrial processes, including metal extraction and corrosion prevention. Additionally, this reaction exemplifies how elements in different states can interchange through simple yet effective electron transactions.