Give tbe principles involved in the manufacture of sulphuric acid by contact procces with equations :

Explanation

Manufacture of sulphuric acid (contact process). It involves following steps:
(i) Production of sulphur dioxide. It is carried out by buming powdered sulphur or roasting of sulphur rich ores.
`S_6+8O_2to8SO_2`
`4FeS_2+11O_2to2Fe_2O_3+8SO_2`
(ii) Oxidation of sulphur dioxide to sulphur trioxide
`2SO_2(g)+O_2(g)overset(400-500^(@)C)underset(15-12atm) This is the major step to the contact process. For better. For better yield of `SO_3`, conditions required are :
Temperature `=400-450^(@)C`, Pressure =1.5 to 2 atm
Catalyst=Pt asbestos or vanadium pentoxide `V_2O_5`
(iii) Conversion of `SO_3` into `H_2SO_4" "SO_3` is absorbed in conc. `H_2SO_4` to produce oleum or pyrosulphuric acid
`SO_3+underset(conc)(H_2SO_4)tounderset("oleum")(H_2S_2O_7)`
So is not absorbed in water as the reaction is highly exothermic and a mist of acid particles is formed. Sometimes it becomes difficult to handle the operation.
(iv) dilution of oleum and formation of `H_2SO_4` Oleum is diluted with calculated quantity of water to obtain `H_2SO_4` is required concentration
`underset("oleum")(H_2S_2O_7)+underset("water")tounderset("sulphuric acid")(2H_2SO_4)`