(a) Describe the conditions and the steps involved in the manufacture of sulphuric acid by contact process. Write the necessary reactions. (No diagram is required)
(b) Give reasons :
(i) Bond dissociation energy of is less than that of
(ii) Nitric oxide becomes brown when released in air.
(a) Contact process : Burning sulphur in an excess of air
or, By heating sulphide ores like pyrites in an excess of air :
In either case, an excess of air is used so that the produced is already mixed with oxygen for the next stage. This is reversible reaction and the formation of is exothermic in the presence of catalyst at 720K.
This cannot be done by simply adding water to the The reaction is so uncontrollable that it creates a fog of Instead, the is first dissolved in conc.
The product is known as fuming sulphuric acid or oleum to which water is added to get
(b) (i) Bond dissociation energy of is less than that of because of large electron-electron repulsion among the lone pair in molecule.
(ii) Nitric oxide becomes brown when released in air because of the formation of gas.