Problem 7 - Chemistry in 30 days

Question

In the extraction of iron, \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) is reduced by (a) carbon dioxide (b) aluminum (c) carbon and carbon monoxide (d) electrolytic reduction

Step-by-Step Solution

Answer

The correct answer is (c) carbon and carbon monoxide.

Step 1: Understanding the Problem

The exercise asks which substance is used to reduce iron(III) oxide, \( \mathrm{Fe}_{2} \mathrm{O}_{3} \), in the extraction of iron. This requires knowing the chemical reaction involved in the extraction process.

Step 2: Exploring Reduction Agents

Let's review the potential reduction agents listed in the options: (a) carbon dioxide, (b) aluminum, (c) carbon and carbon monoxide, and (d) electrolytic reduction. In metallurgy, iron is typically reduced using carbon-based agents in a blast furnace.

Step 3: Identifying the Correct Agent

In a blast furnace, \( \mathrm{Fe}_{2} \mathrm{O}_{3} \) is reduced by carbon monoxide, formed during the combustion of carbon in the presence of oxygen. This points towards option (c) carbon and carbon monoxide as the correct choice.

Step 4: Confirm the Reduction Reaction

In the iron extraction process, iron(III) oxide reacts with carbon monoxide as follows: \( \mathrm{Fe}_{2} \mathrm{O}_{3} + 3\mathrm{CO} \rightarrow 2\mathrm{Fe} + 3\mathrm{CO}_{2} \). This confirms that option (c) is indeed the correct reducing method.

Key Concepts

Iron(III) Oxide Reduction

Iron(III) oxide, known chemically as \(\mathrm{Fe}_{2}\mathrm{O}_{3}\), is a vital component in the iron extraction process. It is a reddish-brown compound that serves as a raw material, representing the oxidized state of iron. For iron to be extracted and used in various industries, \(\mathrm{Fe}_{2}\mathrm{O}_{3}\) must undergo a reduction reaction. This involves removing the oxygen from iron oxide to isolate the pure iron.
To achieve this reduction, chemical reactions are initiated that involve a reducing agent. In the case of iron,(III) oxide, the effective reduction is done through carbon monoxide \(\mathrm{CO}\), as it can efficiently strip oxygen atoms away from \(\mathrm{Fe}_{2}\mathrm{O}_{3}\), converting it into iron \(\mathrm{Fe}\) and resulting in carbon dioxide \(\mathrm{CO}_{2}\) as a by-product.
In terms of reactions, it's represented as:

• The initial equation: \(\mathrm{Fe}_{2}\mathrm{O}_{3} + 3\mathrm{CO} \rightarrow 2\mathrm{Fe} + 3\mathrm{CO}_{2}\)

Understanding this process is crucial as it forms the basis for efficiently extracting iron on a large scale.

Blast Furnace Process

The blast furnace is a highly effective industrial mechanism used to extract iron from its ores. It’s a towering structure often lined with heat-resistant bricks and designed to operate continuously.
Creative engineering allows the blast furnace to process massive quantities of materials, making it the method of choice in industrial iron manufacturing.
To comprehend how a blast furnace functions:

• Iron ore, coke (a form of carbon), and limestone are introduced from the top of the furnace.
• Heated air is blasted into the lower part of the furnace, causing the coke to burn and generate heat.
• This process produces carbon monoxide which rises through the furnace and reduces the iron(III) oxide into iron and carbon dioxide.
• The limestone acts as a flux, combining with impurities to form slag which can be removed separately.

The entire operation results in molten iron collecting at the bottom of the furnace, while slag floats above it and can be tapped off.
This ingenious arrangement allows for a continuous flow of solid inputs and molten and gaseous outputs, signaling a model of efficiency in metallurgical engineering.

Carbon Monoxide as Reducing Agent

Carbon monoxide is a critical player in the reduction of iron(III) oxide within the blast furnace. Its utilization is pivotal because of its high affinity for bonding with oxygen.
Here's why carbon monoxide is chosen for this task:

• Formation: During the combustion of coke in the oxygen-rich lower part of the furnace, carbon reacts with oxygen to form \(\mathrm{CO}\) (carbon monoxide). \(\mathrm{2C} + \mathrm{O}_{2} \rightarrow 2\mathrm{CO}\)
• Reduction Power: Once formed, carbon monoxide rises through the furnace, meeting iron(III) oxide. Here, it acts as a reducing agent, stripping away oxygen from \(\mathrm{Fe}_{2}\mathrm{O}_{3}\) and forming \(\mathrm{CO}_{2}\). \(\mathrm{Fe}_{2}\mathrm{O}_{3} + 3\mathrm{CO} \rightarrow 2\mathrm{Fe} + 3\mathrm{CO}_{2}\)
• Efficiency: The process effectively liberates pure iron from the ore while continuously regenerating the necessary heat and chemical environment.

The continuous production and utilization of carbon monoxide within the blast furnace are essential, as they ensure a steady supply of reducing agent to facilitate the transformation of iron oxide to iron.