Problem 15 - A Complete Resource Book in Chemistry for JEE Main

Question

Identify the reaction that does not take place during the smelting process of copper extraction. (a) \(\mathrm{Cu}_{2} \mathrm{O}+\mathrm{FeS} \longrightarrow \mathrm{Cu}_{2} \mathrm{~S}+\mathrm{FeO}\) (b) \(\mathrm{FeO}+\mathrm{SiO}_{2} \longrightarrow \mathrm{FeSiO}_{3}\) (c) \(2 \mathrm{Cu}_{2} \mathrm{~S}+3 \mathrm{O}_{2} \longrightarrow 2 \mathrm{Cu}_{2} \mathrm{O}+2 \mathrm{SO}_{2} \uparrow\) (d) \(2 \mathrm{FeS}+3 \mathrm{O}_{2} \longrightarrow 2 \mathrm{FeO}+2 \mathrm{SO}_{2} \uparrow\)

Step-by-Step Solution

Answer

The reaction (d) does not occur during the smelting process of copper extraction.

Step 1: Understanding Smelting Process

In the extraction of copper, smelting is a process used to extract copper from its ores by applying heat to melt the ore minerals into a metal. During this process, chemical reactions occur that separate the metal from the impurities.

Step 2: Analyzing Each Reaction

We need to identify reactions that typically take place during smelting. (a) Copper(I) oxide reacts with iron sulfide: This reaction occurs to form copper(I) sulfide and iron oxide, common in the smelting process. (b) Iron oxide and silicon dioxide react to form iron silicate: This is a slag formation process, common in smelting. (c) Copper(I) sulfide and oxygen react to form copper(I) oxide and sulfur dioxide: This oxidation of sulfides to oxides occurs in smelting. (d) Iron sulfide reacting with oxygen: This forms iron oxide and sulfur dioxide, typical in roasting but not in the smelting of copper.

Step 3: Identify Non-Smelting Reaction

Both reactions (c) and (d) are oxidations involved in roasting rather than smelting. Smelting usually involves reactions (a) and (b) where sulfides and oxides form metals and slags. Thus, reaction (d) does not occur during the smelting of copper.

Key Concepts

Smelting Process

Smelting is a key stage in the extraction of copper from its ores. It involves heating ore in order to extract the metal in pure form. Essentially, copper smelting requires high temperatures to melt the ore. By separating the precious metal from impurities, this process produces a more refined end product.

During smelting, the applied heat causes chemical changes. These changes help separate metal compounds from non-metal components, often resulting in a molten liquid state of the desired metal. Smelting effectively reduces the ores into a single metal, making it essential for mining industries. The process ensures that unwanted materials are either separated or removed, thus refining the metal yield.

Some common reactions observed during smelting include the conversion of metal oxides to free metals and the formation of secondary compounds like iron silicate from existing materials.

Chemical Reactions in Metallurgy

The processing of metals from ores involves complex chemical reactions of metallurgy. These reactions facilitate the conversion of minerals into metal products.

- **Reduction Reactions**: These involve removing oxygen from compounds, such as turning copper oxides into pure copper. - **Oxidation Reactions**: Some metals need to oxidize, i.e., react with oxygen, to facilitate further separation processes. - **Sulfide Reactions**: Reactions involving sulfides are pivotal, turning less stable compounds into stable metal states.

Understanding these reactions is crucial. They indicate how elements transform within different processes, including smelting. Knowing which reactions occur ensures that the smelting process is more efficient and productive. Each reaction has a specific purpose, aiding in separating metal from slag or producing the desired metallic substance.

Slag Formation

Slag is a by-product formed during the smelting process. It is essentially composed of gangue minerals like silica, which react with flux materials and oxides.

Slag performs several roles in metal extraction:

• Acts as a protective layer over the molten metal, reducing oxidation and energy loss.
• Traps impurities that can then be removed from the final metal product.
• Facilitates the safe disposal of waste materials, ensuring the purity of the metal extracted.

Slag in copper smelting often results from adding substances like iron oxide and silicon dioxide. These combine to form iron silicate slag, which is non-metallic and can be easily removed. Understanding slag formation is key to improving the efficiency of the smelting process, as it aids in the effective separation of unwelcome impurities.