Write a balanced chemical equation for -

(i) The formation of aluminium at the cathode, during the electrolysis of alumina

(ii) Action of heat on aluminium hydroxide.

Choose the correct answer from the options A, B, C and D given. The reason for using aluminium in the alloy duralumin is:

A: Aluminium is brittle
B: Aluminium gives strength
C: Aluminium brings lightness
D: Aluminium lowers melting point

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.

Arrange the following according to the instructions given in the bracket: K, Pb, Ca, Zn
[In the increasing order of reactivity]