In the manufacture of sulphuric acid write :
(i) The equation with condition for oxidation of `SO_(2)` to `SO_(3)`.
(ii) Formation of Oleum from `SO_(3)`.

Explanation

(i) `2SO_(2)(g) + O_(2) rarr 2SO_(3)`
Any one conditions :
Temperature = 270 K or Pressure = 2bars or Catalyst `= V_(2)O_(5)`
(ii) `SO_(3) + H_(2)SO_(4) rarr H_(2)S_(2)O_(7)` (Oleum)
(i) In manufacturing of `H_(2)SO_(4)`, equation with condition for oxidation of `SO_(2)` to `SO_(3)` are as follows :
Equations : `2SO_(2) + O_(2) overset("catalyst")hArr 2SO_(3)`.
Condition :
(a) Oxidation is always done by passing warm `SO_(2)` bearing gas, through a catalyst like , V, K, NA, Cs, `SIiO_(2)` etc. Now a days `V_(2)O_(5)` (Vanadium penta oxide) is perfered, as it is cheaper and not poisoned by impurities.
(b) Low temperature (about 720 K).
(c ) Excess of air.
(d) High pressure (about 2 atm).
(ii) Formation of Oleum from `SO_(3)` :
`SO_(3) + H_(2)SO_(4) rarr underset("(Oleum)")(H_(2)S_(2)O_(7))`
`SO_(3)` cannot absorbed in water because it produces dense fog, while `H_(2)SO_(4)` absorbs `SO_(3)` to give oleum.