Write balanced chemical equation for the following reaction: Reduction of copper[II] oxide by hydrogen.

Give the appropriate term defined by the statement given : The process by which certain ores, specially carbonates are converted to oxides in the absence of air.

Answer the following questions based on the extraction of aluminium from alumina by Hall- Heroult's Process.

(i) What is the function of cryolite used along with alumina as the electrolyte.

(ii) Why is the powdered coke sprinkled on top of the electrolyte.

(iii) Name the electrode from which aluminium is collected.

Give the chemical formula of :

(i) Bauxite

(ii) Cryolite

(iii) Sodium aluminate