Answer the Following :
(i) What is the role of cryolite in the metallurgy of aluminium?
(ii) Differentiate between roasting and calcination.
(iii) What is meant by the term 'chromatography' ?

Explanation

(i) To decrease the melting point of mixture and to increase the conductivity of alumina.
(ii)
(iii) it was originally derived from the Greek word-chroma meaning colour and graphy meaning writing because it was first used for the separation of coloured substances into individual components. the term chromatography has lost its original meaning and this method is widely used for separation, purification and characterization of the components of a mixture whether coloured or colour less.