Question

Assertion: Lead, tin, and bismuth are purified by liquation method.
Reason: Lead, tin, and bismuth have low m.p. as compared to impurities.
Read the above assertion and reason and choose the correct option regarding it.
A. Both Assertion and Reason are correct and Reason is the correct explanation for assertion
B. Both Assertion and Reason are correct but Reason is not the correct explanation for assertion
C. Assertion is correct but Reason is incorrect
D. Both Assertion and Reason are incorrect

Answer 1

When we extract a metal, it is usually contaminated with several impurities. So, to get a completely pure metal, we practice various techniques based on the chemical and physical differences between metal and the impurity. Liquation is one of such techniques.

Complete step by step answer:
Let us first talk about the process of liquidation. Liquation is a process by which a metal with a low melting point is separated from its impurities. Here, the impure metal is heated on a sloping hearth of a furnace, such that the metal with a low melting point is melted and flows away from the infusible impurities, and is collected in a chamber placed below the sloping hearth furnace.
So it is clear that in this process the melting point of impurities must be higher than the melting point of metals. Because, while heated and partial melting is carried out on a sloping furnace the impurity should not melt more easily or at an equal rate with the metal. If anything like that happens the method of refining becomes completely useless. Hence, this refining technique is only performed in a condition such that the impurity should melt only after a specific period from the melting time of the metal.
Examples of metals with low melting points include Lead (Pb) , tin (Sn) , and bismuth (Bi) .
Now, from the above-mentioned explanations, it is clear that both the assertion and reason are correct. Because, lead, tin, and bismuth possess a low melting point and the refining of such metals is carried out through the process of liquidation as their melting point is lower than the impurities.

So, the correct answer is Option A.

Note: Liquidation has several limitations as we saw that only metals with a low melting point can be refined using this method. This process also is not completely accurate as there are chances for the mixing up of some of the impurities with molten metal and as a result, complete purification is not always possible. Liquation has previously been used to remove antimony minerals from ore and to isolate silver from copper using lead as a solvent.