Question

The chemical processes in the production of steel from haematite ore involve (a) reduction (b) oxidation (c) reduction followed by oxidation (d) oxidation followed by reduction

Short answer

Reduction followed by oxidation (c).

Step-by-step solution

Understanding Haematite Ore

Haematite is an iron ore with the formula \( \text{Fe}_2\text{O}_3 \). It is one of the primary sources of iron for steelmaking. The process of extracting iron from haematite involves transforming the iron ore to a pure form of iron.

Initial Processing – Reduction

In the blast furnace, haematite reacts with carbon monoxide (\( \text{CO} \)) produced from coke. The reaction reduces \( \text{Fe}_2\text{O}_3 \) to molten iron. This can be described by the equation: \[ \text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2 \] Here, iron oxide is reduced (gain of electrons) as oxygen is removed from the ore.

Understanding Reduction and Oxidation

Reduction is the process of gaining electrons or loss of oxygen, whereas oxidation is the loss of electrons or gain of oxygen. The above reaction involves the reduction of iron oxides to iron.

Final Processing – Oxidation of Impurities

After reduction, steelmaking involves removing impurities like carbon, sulfur, and silicon, typically by blowing oxygen through the molten iron. The reactions involved are oxidative, as they involve combining these impurities with oxygen to form oxides, which are then removed.

Conclusion – Process Sequence

Based on the explanation, the production of steel from haematite ore involves reduction followed by oxidation. The sequence includes reducing the iron ore to obtain raw iron and then oxidizing impurities in the iron.

Key concepts

Iron Extraction

Iron extraction is a vital step in the production of steel, beginning with the separation of iron from its natural sources. The primary focus is on the transformation of iron ore, specifically haematite, into pure iron. This process is conducted in a blast furnace, where a series of chemical reactions occur.

• Haematite, with the formula \( \text{Fe}_2\text{O}_3 \), is combined with coke, a form of carbon, in the furnace.
• Carbon in the coke reacts with oxygen to produce carbon monoxide \( \text{CO} \), which acts as a reducing agent for the iron ore.
• The haematite reacts with carbon monoxide, as shown in the reaction: \( \text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2 \).

This reaction highlights the reduction process, where iron oxide loses oxygen and gains electrons, becoming pure molten iron. Understanding this initial step of iron extraction is crucial for grasping how the base material for steel is produced.

Haematite Ore

Haematite ore is one of the key ingredients in steelmaking due to its high iron content and abundance. Recognized by its reddish-brown coloration, haematite has the chemical composition \( \text{Fe}_2\text{O}_3 \). This composition makes it one of the most efficient and cost-effective sources for iron extraction.

• Haematite's abundance and high iron content make it preferable among other forms of iron ore.
• It's mined on a large scale and transported to processing plants, where it undergoes the reduction process in a blast furnace.

Haematite plays a fundamental role in modern steel production as its properties are well-suited to be oxidized and reduced efficiently. It's the preferred choice when a significant yield of iron is required, ultimately leading to the large-scale production of steel.

Reduction and Oxidation Processes

In steel production, the reduction and oxidation processes play pivotal roles. These complementary processes represent the dual steps required to convert iron ore into usable iron and ultimately steel.

Reduction

The initial phase in the blast furnace is the reduction of iron ore. Here, reduction refers to the loss of oxygen by the iron oxide, facilitated by carbon monoxide:

• This involves electrons being transferred to the iron, effectively turning it into its metallic state.

Oxidation

Post-reduction, the raw iron contains impurities such as carbon, sulfur, and silicon.

• These elements are oxidized, meaning they gain oxygen,l to form various oxides that can be removed.
• This stage purifies the molten iron, transforming it into steel ready for further processing.

Oxidation and reduction processes are essential for achieving the purity required in steel. The intricacy of these chemical alterations highlights both the complexity and importance of each step in the steel-making journey.