While extracting an element from its ore, the ore is grind and leached with dil KCN solution to form the soluble product potassium argentocyanide. The element is

Options

A. Mn
B. Cr
C. Fe
D. Ag

Answer

D

Explanation

Silver is obtained form its low grade ores by leaching them whith a dulute solution of sodium cyanide, when the silver compounds dissolve forming the soluble complex argentocyanide ion:
`Ag_(2)S + 4 NaCNhArr2Na [Ag (CN)_(2)] + Na_(2)S`
Air is blown into the mixture to oxidize the sodium sulphide to sulphate and thereby make the reversible reaction proceed completely to the right.
`4 Na_(2)S + 5O_(2) + 2H_(2)O rarr 2 Na_(2)SO_(4) + NaOH + 2S`
The silver is precipitated form the solution by adding some electropositive metal, usually Zn or AI:
`2Na [Ag(CN)_(2)] + Zn rarr 2 Ag + Na_(2) [Zn(CN)_(4)]`