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Lead obtained form galena (PbS) by air r...

Lead obtained form galena `(PbS)` by air reduction or carbon reduction process contains base metal `(Cu, Bi, Sn, As)` as impurities, due to the which lead becomes hard and brittle.
`Zn-Ag` alloy formed in the upper layer of molten lead is skimmed off from the surface of the molten lead by perforated ladles. This alloy contains lead as impurity. This impurity of `Pb` is removed by

A

Distillation

B

Cupellation

C

Liquation

D

Bett's electrolysis

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To solve the question regarding the removal of lead impurity from the zinc-silver alloy formed during the extraction of lead from galena, we can follow these steps: ### Step-by-Step Solution: 1. **Understanding the Context**: - Lead is obtained from galena (PbS) through reduction processes, which can introduce impurities such as copper (Cu), bismuth (Bi), tin (Sn), and arsenic (As). - During the extraction, a zinc-silver alloy forms on the surface of molten lead, which contains lead as an impurity. 2. **Identifying the Impurity Removal Process**: - The question asks how to remove lead from the zinc-silver alloy. The appropriate method for this is crucial to understand. 3. **Explaining the Process**: - The process used to remove lead from the zinc-silver alloy is known as **liquefaction**. - Liquefaction is a refining process that is particularly effective for metals with low melting points that are associated with high-melting impurities. 4. **Describing the Liquefaction Process**: - In liquefaction, the impure metal (in this case, the zinc-silver alloy) is heated on a sloping hearth of a furnace. - As the temperature rises, the pure metal (zinc and silver) melts and flows down the slope due to its lower melting point. - The higher melting point impurities, such as lead, remain behind on the hearth, effectively separating them from the desired alloy. 5. **Conclusion**: - Therefore, the method to remove lead impurity from the zinc-silver alloy is through the process of **liquefaction**. ### Final Answer: The impurity of lead is removed by **liquefaction**. ---
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