Describe the role of the following :
(i) NaCl in the extraction of silver from a silver ore
(ii) Iodine in the refining of titanium
(iii) Cryolite in the metallurgy of aluminium

Explanation

(i) Role of NaCl in the extraction of silver is to do the leaching of silver ore in the presence of air from which the silver is obtained later by replacement
`4 Ag(s) + 8CN^(-)(aq)+2 H_(2)O(aq)+O_(2)(g) to 4[Ag(CN)_(2)]^(-)(aq) +4 OH^(-)(aq)`
` 2[Ag(CN)_(2)]^(-)(aq)+Zn(s) to 2 Ag (s)+[Zn(CN)_(4)]^(2-)(aq)`
(ii) Iodine is heated with Titanium to form a voilatile compound which on further heating decompose to give pure titanium
`T_(i)("impure")+2I_(2) toT_(i)I_(4) to T_(i)("Pure")+2I_(2)`
(iii) Cryolite lowers the melting point of the mixture and improves the electrical conductivity of the cell .