(a) Write the principle involved in the vapour phase refining of metals.
(b) Write the name of the metal refined by each of the following processes :
(i) Mond process (ii) van Arkel method
(c ) What is the role of depresent in froth floatation process ?

Explanation

(a) Vapour phase refining : In this method, crude metal is freed from impurities by first converting it into a suitable volatile compound by heating it with a specific reagent at a lower temperature and then decomposing the volatile compound at some higher temperature to give pure metal.
(c ) Depressant is to prevent one type of sulphide ore particles from forming the froth with air bubbles. Example : NaCN is used as a depressant to separate lead sulphide (PbS) ore from Zinc Sulphide (ZnS).
`4NaCN + ZnS rarr underset("Prevent from forming the forth)")underset("(Complex formed and")(NO_(2)[Zn(CN_(4))]+Na_(2)S)`