Contact process
* Contact process is an industrial process of producing sulphuric acid.
* SO3 obtained in this process is added to sulphuric acid to form oleum (H2S2O7)
SO3(g)+H2SO4(l) → H2S2O7(l)
* SO3 is not directly dissolved in water to form sulphuric acid because it resluts in the formation of dense fog of sulphuric acid which is difficult to condense.
* Also, addition of sulphur trioxide to water is highly exothermic in nature, which also increases the challenges in handling the process.