(i) Name the method of refining of nickel
(ii) What is the role of cryolite in the extraction of aluminium ?
(iii) What is the role of limestone in the extraction of iron from its oxides ?

Explanation

(i) Mond process.
(ii) It makes aluminium a good conductor of electricity and it lowers the fusion (M.P) temperature both from 2323 k to about 1140 K.
(iii) At 1123k, limestone decomposes to form CaO and `CO_(2).` CaO act as flux and combine silica (impurity) to form calcium silicate slag.
`CaCO_(3) (s)overset(1123k)(to)CaO(s) + CO_(2)(g)`
`CaO(s) + SiO(s) to CaSiO_(3) " Calcium silicate (slag)"`