We know that sulphur dioxide reacts with water to form sulphurous acid(H2SO3). But in preparation of sulphuric acid by Contact process, in washing chamber ,why sulphur dioxide does not react with water?

Asked by Upkar | 24th Oct, 2013, 02:33: PM

Expert Answer:

In the manufacture of sulphuric acid by Contact process, in the first step sulphur dioxide is produced by roasting metallic sulphides in air.

4FeS2   + 11O2 ? 2Fe2O3 + 8SO2

In the second step, sulphur dioxide produced is oxidized to SO3 in the presence of catalyst V2O5 at 400-4500C.

2SO2 + O2 ------> 2SO3

Sulphur trioxide from the contact tower is passed onto absorption tower where it is absorbed by descending stream of 98% sulphuric acid to form oleum. It is then diluted with water to get sulphuric acid of desired concentration.
SO3 + H2SO4 -----> H2S2O7
H2S2O7 + H20 -----> 2H2SO4


Answered by Vaibhav Chavan | 25th Oct, 2013, 10:57: AM

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