Understanding the Reaction: $\text{ZnO} + \text{C} \rightarrow \text{Zn} + \text{CO}$

The given reaction, $\text{ZnO} + \text{C} \rightarrow \text{Zn} + \text{CO}$, is an example of a redox reaction. Redox reactions involve the transfer of electrons, resulting in changes in the oxidation states of the elements involved. One substance is reduced, and another is oxidized.

Identifying Oxidation and Reduction

To determine what role Carbon ('C') plays in this reaction, we need to look at the oxidation states of the elements in the reactants and products.

• Reactants:
  • In $\text{ZnO}$ (Zinc Oxide), Oxygen typically has an oxidation state of -2. Since $\text{ZnO}$ is a neutral compound, the oxidation state of Zinc (Zn) must be +2 to balance the -2 charge from Oxygen. So, Zn is +2, O is -2.
  • In elemental Carbon (C), the oxidation state is 0.
• Products:
  • In elemental Zinc (Zn), the oxidation state is 0.
  • In $\text{CO}$ (Carbon Monoxide), Oxygen typically has an oxidation state of -2. For the compound to be neutral, the oxidation state of Carbon (C) must be +2. So, C is +2, O is -2.

Tracking Oxidation State Changes

Now let's see how the oxidation states change from reactants to products:

• Zinc (Zn) goes from an oxidation state of +2 in $\text{ZnO}$ to 0 in elemental Zn. The oxidation state decreases. This is a reduction.
• Carbon (C) goes from an oxidation state of 0 in elemental C to +2 in $\text{CO}$. The oxidation state increases. This is an oxidation.

We can summarize the changes in a table:

Defining Oxidizing and Reducing Agents

In a redox reaction:

• An oxidizing agent is the substance that causes oxidation in another substance. It does this by accepting electrons, and in the process, it itself gets reduced.
• A reducing agent is the substance that causes reduction in another substance. It does this by donating electrons, and in the process, it itself gets oxidized.

Conclusion: Role of Carbon in $\text{ZnO} + \text{C}$ Reaction

In the reaction $\text{ZnO} + \text{C} \rightarrow \text{Zn} + \text{CO}$, we observed that:

• Zinc ($\text{Zn}^{2+}$ ions in $\text{ZnO}$) is reduced to elemental Zinc ($\text{Zn}$).
• Carbon (C) is oxidized to Carbon Monoxide ($\text{CO}$).

Since Carbon is oxidized and it causes Zinc Oxide to be reduced, Carbon acts as the reducing agent in this reaction. It donates electrons to the zinc ions in ZnO, reducing them, while Carbon itself gains oxygen (and loses electrons) and gets oxidized.

Therefore, in the reaction $\text{ZnO} + \text{C} \rightarrow \text{Zn} + \text{CO}$, 'C' acts as a reducing agent.

Revision Table: Key Concepts in Redox Reactions

Additional Information: Uses of Carbon as a Reducing Agent

Carbon is a common and inexpensive reducing agent used in various industrial processes, particularly in the extraction of metals from their oxides. This process is called smelting.

• Metal Extraction: Carbon (often in the form of coke or charcoal) is widely used to reduce metal oxides like $\text{ZnO}$, iron oxides (e.g., in blast furnaces), and lead oxides to obtain the pure metal. This is because carbon can effectively remove oxygen from the metal oxide.
• High Temperatures: These reactions often require high temperatures to proceed, as the carbon reacts vigorously with the metal oxide at elevated heat.
• Carbon Monoxide Formation: The product formed from carbon's oxidation is usually carbon monoxide ($\text{CO}$), as seen in the reaction with ZnO, or carbon dioxide ($\text{CO}_2$), depending on the conditions and the amount of oxygen available. Carbon monoxide itself can also act as a reducing agent.

The reaction $\text{ZnO} + \text{C} \rightarrow \text{Zn} + \text{CO}$ is a classic example of how carbon is used to reduce metal oxides to extract the metal.