Oxides of the various metals are converted into metal by heating but not in :

Why should the metal sulphides and carbonates be converted to metal oxides in the process of extraction of metal from them? 

Auto-reduction is employed in the metallurgy of :

In order to obtain 1 tonne of aluminium, 4 tonnes of bauxite, 150 kg of sodium hydroxide and 600 kg of graphite is required. The aluminium compound in bauxite is aluminium oxide and the main impurity is iron (III) oxide, Aluminium is obtained by the electrolysis of aluminium oxide dissolved in cryolite.
In construction work, why is the alloy of aluminium(duralumin) used rather than pure aluminium?

Differentiate between roasting and calcination.

Name the following:
Two metals which are used for the reduction in metallurgical process.

The order of processes involved in the dressing of an ore are :
(i) grinding and crushing           (ii) hand picking                (iii) pulverization

Describe the extraction of three different elements using carbon as the reducing agent.

The reduction of an oxide by aluminium is called:

Although carbon and hydrogen better reducing agents but they are not used to reduced metallic oxides at high temperatures. Why?