Concentration, Oxidation and Reduction — Prelims Questions

Which of the following methods is based on the difference in wetting properties of ore and gangue particles?

Which of the following statements is INCORRECT regarding roasting and calcination?

In the extraction of aluminium by the Hall-Héroult process, the role of cryolite ($Na_3AlF_6$) is to:

Which of the following reactions represents auto-reduction?

In the leaching of gold with $NaCN$ solution, what is the role of oxygen?

Which of the following is an example of an acidic flux used in smelting?