(i) Why Sulphuric acid is called the 'king of chemicals'?
(ii) Name the gas evolved when :
      (a) Concentrated Sulphuric acid acts on Sulphur.
      (b) Dilute Sulphuric acid acts on Sodium carbonate.
(iii) State the colour change you would observe on adding concentrated sulphuric acid to :
      (a) Blue Copper sulphate crystals.
      (b) Colourless cane-sugar crystals.

(a) Write chemical equations for the reactions involved in obtaining pure alumina from the mineral bauxite which has impurities of iron oxide and silica.
(b) Draw a labelled diagram of the electrolytic tank cell used for the extraction of aluminium from alumina.

(a) What is corrosion of metals? Name one metal which does not corrode and one which corrodes on being kept in atmosphere.
(b) How will you show that the rusting of iron needs oxygen and moisture at the same time?

(a) What is an 'activity series' of metals? Arrange the metals Zn, Mg, Al, Cu and Fe in a decreasing order of reactivity.
(b) What would you observe when you put
       (i) Some zinc pieces into blue copper sulphate solution?
       (ii) Some copper pieces into green ferrous sulphate solution?
(c) Name a metal which combines with hydrogen gas. Name the compound formed.

(a) Name one main ore of Aluminium. Write its formula. Which two main impurities are associated with this ore?
(b) Describe with chemical equations, the method employed for the enrichment of the above named ore.