Name two most important allotropes of Sulphur. Which one of the two is stable at room temperature? What happens when the stable form is heated above 370 K?

OR

(i) Write the conditions to maximise the yield of by contact process.

(ii) Why is <<for in water?

Sulphur has many different allotropes out of these the most common ones include Orthorhombic (α – Sulphur) and Monoclinic Sulphur (β – Sulphur). Orthorhombic has puckered ring of Sulphur containing 8 atoms. While the later one has long needles, here all the 8 atoms of the Sulphur are not packed nicely.

Rhombic form of the Sulphur is more stable as compared to the Monoclinic form.

When the most stable form of Sulphur is heated at above 370 K, it gets converted in to Monoclinic form and forms needle-like structures.

OR

(i) Sulphuric acid is manufactured by the process called Contact Process. The process involves 3 steps:

a) Sulphur or Sulphide ores are burnt to produce Sulphur dioxide ().

b) The produced Sulphur dioxide () is converted into Sulphur trioxide () by the catalyst ).

c) Oleum ) is formed when Sulphuric acid is adsorbed by .

Finally, dilution of Oleum by water gives Sulphuric acid. The yield of Sulphuric acid is dependent on the oxidation of Sulphur dioxide () by Oxygen to form . The yield of Sulphuric acid can be achieved by lowering the temperature and increasing the pressure.

ii) In aqueous solution, Sulphuric acid ionises in two steps:

It is easier to release a proton from Sulphuric acid than a charge species (). Therefore, is much smaller than .