NCERT Class XII Chemistry
Chapter - General Principle of Process of Isolation of Elements
Questions with Solutions
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Question : 1
Total: 31
Copper can be extracted by hydrometallurgy but not zinc. Explain.
Solution:
The E 0 of zinc ( Z n 2 + / Z n = − 0.76 V ) is lower than that of copper ( C u 2 + / C u = + 0.34 V ). Hence, zinc can displace Cu from solutions of C u 2 + ions.
Z n ( s ) + C u 2 + ( a q ) → Z n 2 + ( a q ) + C u ( s )
But to displace zinc from solution ofZ n 2 + ions, we need a metal more Al reactive than it, i . e , Al ( E 0 A l 3 + ∕ A l = − 1.66 V ) , Mg ( E 0 M g 2 + ∕ M g = − 2.37 V ) , Ca ( E 0 C a 2 + ∕ C a = − 2.87 V ) , K ( E 0 K + ∕ K = − 2.93 V ) etc.
But all these metals react with water forming their corresponding ionswith the evolution ofH 2 gas. Hence, Al, Mg, etc. cannot be used todisplace zinc from the solution of Z n 2 + ions. Thus, copper can be extractedby hydrometallurgy but notzinc.
But to displace zinc from solution of
But all these metals react with water forming their corresponding ionswith the evolution of
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