Name the chief forms of the occurrence of the following in the earth crust:
(a) aluminium,           (b) calcium,    (c) sodium,          (d) lead.

Sodium metal cannot be obtained by the electrolysis of aqueous sodium chloride solution.

Write the chemical reactions involved in the extraction of metallic silver from argentite.

Silver ores and native gold have to be leached with metal cyanides. Suggest a reason for this.

Describe the principle of froth floatations process. What is the role of stabilizer and of a depressant? Give one example of each. 

Differentiate between 'minerals' and 'ores'.

State briefly the principles which serve as basis for the following operations in metallurgy:
(i) Froth floation process.
(ii) Zone refinnting.
(iii) Refining by liquation.

What chemical principle is involved in choosing a reducing agent for gettting the metal from its oxide ore? Consider the metal oxides, Al₂O₃ and Fe₂O₃ and justify the choice of reducing agent in each case.