Question

Four metals and their methods of refinement are given.
(i) $Ni,Cu,Zr,Ga$
(ii) Electrolysis, Van Arkel process, zone refining, Mond's process

Choose the right method for each.

• A. $Ni$; Electrolysis, $Cu$; Van Arkel process, $Zr$; Zone refining, $Ga$; Mond's process
• B. $Ni$; Mond's process, $Cu$; Electrolysis, $Zr$; Van Arkel process, $Ga$; Zone refining
• C. $Ni$; Mond's process, $Cu$; Van Arkel process, $Zr$; Zone refining. $Ga$; Electrolysis
• D. $Ni$; Electrolysis, $Cu$; Zone refining, $Zr$; Van Arkel process, $Ga$; Mond's process

Answer 1

Answer: (B)

$Ni$; Mond's process, $Cu$; Electrolysis, $Zr$; Van Arkel process, $Ga$; Zone refining

Mond’s Method: It is specially used for $Ni$. The Vapour phase refining of $Ni$ on heating in a stream of $CO$ forms Volatile $Ni(CO{)}_4$. These vapours when subjected to still higher temperature, decompose to give pure metal.

Electrorefining: Anode - Impure copper or crude copper; Cathode - Pure copper. When electric current is passed through the electrolyte, the anode gradually dissolves and pure copper is deposited on the cathode which gradually grows in size. The impurities like $Fe,Zn,Ni$ etc dissolve in the solution as sulphates while gold, silver, platinum settle down below the anode as anode mud.

Van-Arkel method: This method is used for ultrapure metals like $Ti,Zr$ etc. The metal is converted into its volatile stable compound such as $Ti{l}_4$, leaving behind impurities. The stable volatile compound thus formed is decomposed to get the pure metal.

Zone Refining (Fractional Crystallisation): This method is employed to get metal of very high purity i,e. ultra pure samples of $Ge,Si,B,Ga,In$. This method is based on the fact that impurities are more soluble than the pure metal in the melt .