Question

ASSERTION: The metals - copper, silver and lead are electro refined but $K$, $Na$ and $Ca$ are not.
REASON: As $K$ , $Na$ and $Ca$ are more reactive so their reduction is not easy while $Cu$ , $Ag$ and $Pb$
have more reduction potential than hydrogen ions.
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

To answer this question, you must be aware of the reactivity of the given elements. The more the element will be reactive, less will be its capacity to get reduced and hence will have less reduction potential as compared to Hydrogen ion. And hence they will not be electro refined. But instead, if the element will be less reactive then it will be easily reduced and hence will have more reduction potential than Hydrogen ion. And therefore, it will be electro refined.

Complete answer:
Step 1: Firstly, we will compare the reactivity of the given elements. And we will find that $K$ (potassium) , $Na$ (sodium) , $Ca$ (calcium) are more reactive than $Cu$ (copper), $Ag$ (silver), $Pb$ (lead).
Step 2: So, Potassium, Sodium, and Calcium will have less capacity to get reduced as compared to Copper, Silver and Lead because of the reason that Potassium, Sodium, and Calcium will have less reduction potential than Hydrogen ion whereas Copper, Silver and Lead will have more reduction potential than Hydrogen ion.
Step 3: Potassium, Sodium, and Calcium will not be electro refined whereas Copper, Silver and Lead will be electro refined.
Clearly, we can conclude that the Assertion is correct as well as the reason given for that is also correct because Potassium, Sodium, and Calcium will have less capacity to get reduced as compared to Copper, Silver and Lead because of the reason that Potassium, Sodium, and Calcium will have less reduction potential than Hydrogen ion whereas Copper, Silver and Lead will have more reduction potential than Hydrogen ion. And hence Potassium, Sodium, and Calcium will not be electro refined whereas Copper, Silver and Lead will be electro refined.

Hence, the option A is the correct answer.

Note: Electrolytic refining is a process of refining a metal (mainly copper) by the process of electrolysis. As far as the mechanism of the process is concerned, during electrolysis, a large chunk or slab of impure metal is used as the anode with a thin strip of pure metal at the cathode. In this setup, an electrolyte (metal salt aqueous solution) depending on the metal is often used.