sulphuric acid preparations

Contact Process: (Industrial Manufacture of Sulfuric acid)

STEPS:
1. Sulfur is burned in air or oxygen to produce sulphur dioxide S (s) + O2 (g) → SO2(g)
2. Sulfur dioxide reacts with oxygen to form sulfur trioxide
The reaction is catalyzed by vanadium pentoxide at 450◦C and 2 atmospheres.

3. Sulfur trioxide is bubbled through a previously prepared sulphuric acid to form oleum (fuming
sulphuric acid)
SO3 + H2SO4 ⟶ H2S2O7

4. Oleum is added to water to produce sulphuric acid of the required concentration.
(Oleum is always added to water and not the other way round because the reaction is highly exothermic
and the acid could spit out of the container causing severe burns). H2S2O7 + H2O ⟶ 2 H2SO4

The purpose of towers 1 to 5 from left to right:
a) Tower 1: burn pure sulfur with excess oxygen from air: S8(s) + O2(g) ⇌ 8SO2(g).
b) Tower 2: wash SO2 with water to remove any impurities.
c) Tower 3: dry the SO2 by washing it with sulfuric acid.
d) Tower 4: burn SO2 with oxygen to produce SO3(g).
e) Tower 5: wash SO3 with H2SO4 to remove it as fuming H2SO4.


Chemical Properties of sulfuric acid: oxidizing agent.