Question

The carbon-based reduction method is NOT used for the extraction of (A) tin from \(\mathrm{Sn} \mathrm{O}_{2}\) (B) iron from \(\mathrm{Fe}_{2} \mathrm{O}_{3}\) (C) alurninium from \(\mathrm{Al}_{2} \mathrm{O}_{3}\) (D) magnesium from \(\mathrm{MgCO}_{3} \cdot \mathrm{CaCO}_{3}\)

Short answer

(C) aluminium from \(\mathrm{Al}_{2} \mathrm{O}_{3}\) is extracted using the electrolytic Hall-Héroult process, not carbon-based reduction.

Step-by-step solution

Identify the Extraction Processes

Determine the common extraction process for each given metal from its ore.

Match the Processes with the Metals

For each metal, identify whether carbon-based reduction is typically used.

Recognize the Correct Option

Identify the metal that does not typically undergo carbon-based reduction for extraction from its given ore.

Key concepts

Carbon-based Reduction

Carbon-based reduction is a pivotal metallurgical process used to extract metals from their oxides. This method involves using carbon or carbon-containing compounds as reducing agents to facilitate the removal of oxygen from metals. During this process, the metal oxide is heated in the presence of carbon, which acts as the reductant, at high temperatures leading to the formation of pure metal and carbon dioxide.

In simple terms, the carbon pulls away the oxygen atom from the metal oxide compound. An example of a chemical reaction involved is \( \mathrm{MetalOxide} + \mathrm{C} \rightarrow \mathrm{Metal} + \mathrm{CO}_2 \). Although effective for certain metals such as iron and tin (under high temperatures), this method is not suitable for more reactive metals like aluminum, due to aluminum's high affinity for oxygen and the stability of its oxide.

Importance in Industry

The process is vital due to its cost-effectiveness and scalability, making it highly significant in the industrial production of various metals.

Extraction of Tin

Extracting tin involves processing the ore which is primarily \( \mathrm{SnO}_2 \), also known as cassiterite. To obtain pure tin, smelters use carbon-based reduction, typically in a reverberatory furnace. The carbon in the form of coke acts as the reducing agent to separate the oxygen from the tin.

The simplified chemical equation for this process is \( \mathrm{SnO}_2 + 2\mathrm{C} \rightarrow \mathrm{Sn} + 2\mathrm{CO} \). This method is efficient for tin since it works well with the less reactive nature of tin compared to other metals such as aluminum. After reduction, tin is further purified by electrolytic refining or by treatment with certain acids that remove impurities.

• Simplicity of Process
• High Yields and Purity
• Cost-Effectiveness

Extraction of Iron

Iron extraction is typically performed through a method known as the blast furnace process, which is a form of carbon-based reduction. The predominant source of iron is from the mineral hematite \( \mathrm{Fe}_2\mathrm{O}_3 \). Inside a blast furnace, iron oxide reacts with carbon monoxide, which is produced by burning coke. The reaction can be represented as \( \mathrm{Fe}_2\mathrm{O}_3 + 3\mathrm{CO} \rightarrow 2\mathrm{Fe} + 3\mathrm{CO}_2 \).

The carbon monoxide acts as the reducing agent, and molten iron is produced, which is then tapped from the bottom of the furnace. This traditional method is effective and has been optimized over centuries, leading to it being the primary method for producing iron worldwide.

Relevance to Industrial Production

• Efficiency and Scale
• Utilization of Carbon Monoxide as a Reductant

Extraction of Aluminum

The extraction of aluminum is unique as it doesn't employ carbon-based reduction due to the strong bond between aluminum and oxygen in its oxide form, \( \mathrm{Al}_2\mathrm{O}_3 \), known as alumina. Instead, the Hall-Héroult process is used, which involves the electrolytic reduction of alumina dissolved in molten cryolite.

Through this electrolytic process, aluminum ions receive electrons (get reduced) at the cathode and form molten aluminum, which is then collected at the bottom of the cell. The chemical reaction can be summarized as \( \mathrm{Al}_2\mathrm{O}_3 + 3\mathrm{C} \rightarrow 2\mathrm{Al} + 3\mathrm{CO} \), but this occurs in multiple steps within the electrolytic cell.

This method is energy-intensive yet necessary to break the strong aluminum-oxygen chemical bonds, making it the only commercially viable method to produce high-purity aluminum effectively.

Key Aspects of Aluminum Extraction

• Electrolytic Reduction Process
• Energy Intensive but Effective
• Production of High-Purity Aluminum