Problem 125 - A Complete Resource Book in Chemistry for JEE Main

Question

Copper is extracted from copper pyrites ore by heating in a blast furnace. The method is based on the principle that (a) copper has less affinity for oxygen than sulphur at high temperature (b) sulphur has less affinity for oxygen at high temperature (c) iron has less affinity for oxygen than sulphur at high temperature (d) copper has more affinity for oxygen than sulphur at high temperature

Step-by-Step Solution

Answer

(a) copper has less affinity for oxygen than sulphur at high temperature.

Step 1: Analyze the Principle of Extraction

The extraction of copper from copper pyrites involves a series of steps in which copper is released from its ore. The process relies on the relative affinities of the elements involved (copper, sulfur, and iron) for oxygen.

Step 2: Determine Affinities at High Temperature

Copper is less reactive with oxygen compared to sulfur at high temperatures. This suggests that at high temperatures, sulfur will oxidize more readily, leaving behind copper.

Step 3: Apply the Principle to the Given Options

With the knowledge that copper's affinity for oxygen is less compared to sulfur's at high temperatures, select the option that states copper has less affinity for oxygen than sulfur.

Key Concepts

Copper Pyrites

Copper pyrites, scientifically known as chalcopyrite, is a crucial ore in the extraction of copper. It contains iron, copper, and sulfur, with the chemical formula \( \text{CuFeS}_2 \). This ore is significant in industrial applications due to its abundance and copper content. The process of extracting copper from this ore requires careful handling, as the ore is often a compound of different elements.

When extracting copper, one must separate the desired metal from the other elements in the compound. The presence of sulfur and iron in copper pyrites adds complexity to the extraction process. It necessitates an understanding of chemical reactions and the behavior of these elements at high temperatures. This complexity is managed by utilizing a blast furnace, which allows for controlled heating and separation.

Blast Furnace

A blast furnace is a large industrial installation that is crucial for metal extraction processes, including the extraction of copper from ores like copper pyrites. It is designed to withstand high temperatures and involves the combustion of fuel to heat the ore. This is essential for breaking down the ore into its elemental components.

In a blast furnace, the introduction of air blasts increases the temperature and oxygen levels within the furnace. This enhanced oxidation environment helps in the selective oxidation of sulfur within the copper pyrites. The crucial role of a blast furnace is in providing the necessary conditions—mainly heat and an oxidizing environment—for the desired chemical reactions to occur, allowing elements with different affinities for oxygen to react accordingly.

Affinity for Oxygen

The affinity of an element for oxygen is an essential concept in the extraction of metals from their ores. It describes how readily an element will react with oxygen, forming oxides. In the context of copper pyrites, understanding the affinities of copper, sulfur, and iron for oxygen is vital to efficiently separate copper from the ore.

At high temperatures, elements like sulfur have a high affinity for oxygen, meaning they will oxidize more readily than copper. This principle allows us to control which elements react during the extraction process.

• Copper has less affinity for oxygen, so it remains largely in its metallic state.
• Sulfur, on the other hand, oxidizes readily, forming sulfur dioxide gas.

By exploiting these differences in affinity, we can effectively extract copper by allowing sulfur to be oxidized and removed.

High Temperature Reactivity

When it comes to metal extraction, temperature plays a crucial role in determining the reactivity of different elements. This is particularly significant when dealing with complex ores like copper pyrites.

At elevated temperatures, chemical reactions are more likely to occur, making it easier for certain elements to react and separate from others. In copper extraction, the high temperature provided by a blast furnace ensures that sulfur's high reactivity and affinity for oxygen can be utilized.

• High temperature encourages sulfur oxidation, which helps in removing sulfur from the ore.
• It supports the release of copper in a pure form by minimizing undesired reactions with oxygen.

By understanding the effect of temperature on reactivity, we can effectively manage the extraction process, optimizing the separation of copper from other elements in the ore. High temperature acts as a catalyst, driving the reactions necessary for successful metal extraction.