(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 .