What is the major role of fluorospar (CaF₂) which is added in small quantities in the electrolytic reduction of alumina dissolved in fused cryolite?

Which process is used for the concentration of Bauxite (Al₂O₃.2H₂O)?

Sulphide ores usually concentrated by froth flotation process. Why?

Give one example where hydro-metallurgy is used for metal extraction.

How does NaCN act as a depressant in preventive ZnS from forming the froth?

Ultra pure silicon is needed by electronic industry. By which method of refining, such a high purity silicon is obtained?

Name the oxide ores of (a) iron  (b)  zinc,  (c) manganese  (d) aluminium.

Which method of metal refining is generally used when a metal of high degree of purity is needed?