Describe the manufacture of `H_(2)SO_(4)` by contact process?

Explanation

Sulphuric acid is manufactured by the contact process. It involves the following steps:
Step (i):
Sulphur or sulphide ores are burnt in air to form `SO_(2)`.
Step (ii):
By a reaction with oxygen, `SO_(2)` is converted into `SO_(3)` in the presence of `V_(2)O_(5)` as a catalyst.
`2SO_(2(g)) + O_(2(g)) overset(V_(2)O_(5))to 2SO_(3(g))`
Step (iii) :
`SO_(3)` produced is absorbed on `H_(2)SO_(4)` to give `H_(2)S_(2)O_(7) ` (oleum).
`SO_(3)+ H_(2)SO to H_(2)S_(2)O_(7)`
This oleum is then diluted to obtain `H_(2)SO_(4)` of the desired concentration.
In practice, the plant is operated at 2 bar (pressure) and 720 K (temperature). The sulphuric acid thus obtained is `96-98%` pure.