Which of the following is not correctly matched with respect to the processes involved in the extractive metallurgy of the respective metal ?

Explanation

To determine which of the following options is not correctly matched with respect to the processes involved in the extractive metallurgy of the respective metal, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Option A: Extraction of Aluminium from Bauxite Ore (Al2O3·2H2O)**
- **Processes Involved:**
- **Leaching:** The bauxite ore is treated with sodium hydroxide (NaOH), dissolving alumina to form a soluble complex (NaAl(OH)4).
- **Precipitation:** Carbon dioxide is passed through the solution to precipitate alumina (Al2O3·2H2O).
- **Calcination:** The precipitate is heated to remove water, yielding Al2O3.
- **Electrolytic Reduction:** The molten alumina is subjected to electrolysis to produce aluminum.
- **Conclusion:** This option is correctly matched.

2. **Option B: Extraction of Silver from Argentite Ore (Ag2S)**
- **Processes Involved:**
- **Leaching:** Argentite ore is treated with sodium cyanide (NaCN) to form a soluble complex (NaAg(CN)2).
- **Displacement Method:** A more electropositive metal, such as zinc, is used to displace silver from the complex.
- **Conclusion:** This option is correctly matched.

3. **Option C: Extraction of Lead from Galena (PbS)**
- **Processes Involved:**
- **Flotation Process:** Galena is concentrated using flotation.
- **Roasting:** The concentrated ore is roasted to convert PbS to PbO.
- **Self-Reduction:** PbO reacts with unreacted PbS to produce lead (Pb) and sulfur dioxide (SO2).
- **Conclusion:** This option is correctly matched.

4. **Option D: Extraction of Magnesium from Double Salt (KCl·MgCl2·6H2O)**
- **Processes Involved:**
- **Dehydration:** The double salt is dehydrated by heating.
- **Electrolytic Reduction:** Electrolysis is performed in an aqueous phase.
- **Key Issue:** In aqueous electrolysis, hydrogen ions (H+) are reduced preferentially over magnesium ions (Mg²+) due to their higher reduction potential. Therefore, hydrogen gas (H2) is produced instead of magnesium.
- **Conclusion:** This option is not correctly matched.

### Final Answer:
The option that is not correctly matched with respect to the processes involved in the extractive metallurgy of the respective metal is **Option D**.

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