Match List I with List II

Choose the correct answer from the options given below:

A-III, B-II, C-I, D-IV

The correct answer is option 2. A-III, B-II, C-I, D-IV.

Let us go through each reaction step by step to understand how they correspond to the different processes listed in List II.

A. \( 4M + 8CN^- + 2H_2O + O_2 \overset{\Delta }{\longrightarrow} 4[M(CN)_2]^- + 8OH^- \)

Reaction Description:

In this reaction, \( M \) represents a metal (commonly gold or silver), which reacts with cyanide ions (\( CN^- \)), water, and oxygen. The metal forms a soluble complex, \( [M(CN)_2]^- \), and hydroxide ions (\( OH^- \)) are produced. This reaction is a part of the cyanide process, specifically used for extracting precious metals like gold and silver from their ores.

Process:Cyanide Process (III):

The cyanide process, also known as the MacArthur-Forrest process, is used to extract gold and silver by converting them into soluble complexes that can be easily separated from the ore.

Correct Match: III (Cyanide process).

B. \( Al_2O_3 + 2NaOH + 3H_2O \overset{\Delta }{\longrightarrow} 2Na[Al(OH)_4] \)

Reaction Description:

In this reaction, aluminum oxide (\( Al_2O_3 \)) reacts with sodium hydroxide (\( NaOH \)) and water to form sodium aluminate (\( Na[Al(OH)_4] \)). This reaction is part of the leaching process in the Bayer process, which is used to extract alumina from bauxite.

Process: Leaching (II):

Leaching is a process where a soluble constituent is extracted from a solid material by dissolving it in a suitable solvent. In the Bayer process, sodium hydroxide is used to leach alumina from bauxite.

Correct Match: II (Leaching)

C. \( PbS \overset{\Delta }{\longrightarrow} PbO \)

Reaction Description:

Lead sulfide (\( PbS \)) is heated in the presence of oxygen to form lead oxide (\( PbO \)). This is a typical example of roasting, where sulfide ores are converted into oxides by heating them in the presence of oxygen.

Process: Roasting (I):

Roasting is a metallurgical process involving heating of ore in the presence of oxygen, causing the sulfide ore to convert into its oxide. This is a preparatory step before the ore undergoes further processing.

Correct Match: I (Roasting)

D. \( Cu_2S \overset{\Delta }{\underset{C}{\longrightarrow}} Cu \)

Reaction Description:

In this reaction, copper(I) sulfide (\( Cu_2S \)) is heated, and it undergoes a process called self-reduction or auto-reduction, where it is converted into metallic copper without the need for an external reducing agent. This typically occurs in the presence of a small amount of carbon or just by heating the sulfide in the absence of sufficient oxygen.

Process: Self-Reduction (IV): Self-reduction is a process where a sulfide ore is directly reduced to the metal by heating, often in the presence of its own sulfide, without the need for an external reducing agent.

Correct Match: IV (Self-reduction)

Conclusion:

The correct answer is Option 2: A-III, B-II, C-I, D-IV. Each reaction in List I corresponds to the correct metallurgical process in List II.