(a) Write the principle of vapour phase refining. ltbr. (b) Write the role of dilute NaCN in the extraction of silver. ltBrgt (c) What is the role of collectors in the froth floatation process? Give an example of a collector.

Explanation

(a) Vapour phase refining: The crude metal is freed from impurities by first converting it into suitable volatile compound by heating it with a specific reagent at a lower temperature and then decomposing the volative compound at some higher temperature to give the pure metal.
(b) NaCN oxidises silver to form soluble complex of cyanide while the impurities remain unaffected which are filtered off.
`4Ag+8CN^(-)+2H_(2)O+O_(2)to4{Ag(CN)_(2)]^(-)+4OH^(-)`
this process in known as leaching.
(c) Collectors enchance the non-wettability of the ore particles. Example, Pine oil, Xanthates.