Problem 109 - A Complete Resource Book in Chemistry for JEE Main

Question

The chemical composition of 'slag' formed during the smelting process in the extraction of copper is (a) \(\mathrm{Cu}_{2} \mathrm{O}+\mathrm{FeS}\) (b) \(\mathrm{FeSiO}_{3}\) (c) \(\mathrm{CuFeS}_{2}\) (d) \(\mathrm{Cu}_{2} \mathrm{~S}+\mathrm{FeO}\)

Step-by-Step Solution

Answer

(b) FeSiO_3 is the slag in copper extraction.

Step 1: Understanding Slag Formation

In the extraction of copper, slag is formed during the smelting process. This occurs when impurities in the ore, such as iron, are removed from the molten copper by forming a separate layer. It generally involves the combination of unwanted minerals with flux, often silica, forming a silicate compound.

Step 2: Role of Silica in Copper Smelting

In the smelting process for copper extraction, silica ( SiO_2 ) is added as a flux to the furnace. The purpose of this addition is to react with iron oxide, an impurity in the ore, forming iron silicate ( FeSiO_3 ) as slag. This can easily be removed as waste.

Step 3: Identifying Correct Option

Given the typical process of copper smelting, we expect that silica will react with iron oxides to form the slag compound FeSiO_3 , as we have described. Therefore, the chemical composition of the slag should be FeSiO_3 .

Key Concepts

Slag Formation

In the context of copper extraction, slag formation is a crucial step in the smelting process. During smelting, copper ore is melted to separate impurities from pure copper. Slag is the byproduct that forms when these impurities, typically iron, are combined with a flux. The presence of slag is important because it aids in removing unwanted materials from the metal ore, ensuring high purity of the extracted copper.

The formation of slag involves a chemical reaction where impurities, like iron oxide, react with flux additives to create a separate layer. This layer, which consists mostly of silicate compounds, floats on top of the molten copper. It is then removed. This process not only purifies the copper but also helps to protect the metal from oxidation during smelting. Understanding slag formation is pivotal to grasping the intricacies of copper metallurgy.

Silica Flux

Silica flux plays a fundamental role in the smelting process of copper. Smelting involves heating the copper ore to a point where its components become molten. During this process, impurities must be separated from the copper to achieve a refined product. This is where flux compounds, like silica, come into play.

Silica ( SiO_2 ) is added to the furnace to act as a flux. It specifically reacts with iron oxide impurities, which are commonly found in copper ores. This reaction produces iron silicate ( FeSiO_3 ), a compound that forms part of the slag. The role of silica is vital as it not only aids in purifying the copper by forming this easily removable slag but also enhances the efficiency of the smelting process. Incorporating silica ensures that the copper extracted is of a higher quality, free from major impurities.

Iron Silicate

Iron silicate is a prominent component of slag during copper smelting and is essential for the removal of iron impurities. This compound, FeSiO_3 , results from the reaction between silica flux and iron oxides present in the copper ore. The production of iron silicate is key to the separation process because it forms a layer that is easily skimmed off during smelting.

Iron silicate, by becoming part of the slag, effectively binds the iron and removes it from the molten copper. This process not only purifies the copper but also contributes to the overall efficiency of the smelting operation. By understanding the role of iron silicate in slag formation, one gains insight into how impurities are systematically eliminated from copper ores, leading to high-quality metal production.