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Acids and Alkalis

Manufacture of Sulfuric Acid  -  The Contact Process.

How is Sulfur trioxide made into Sulfuric Acid?


 Sulfur trioxide will dissolve in water to make sulfuric acid.

This is the balanced chemical equation for the reaction of
sulfur trioxide with water.

sulfur trioxide     +      water       arrow    sulfuric acid
        SO3(g)         +      H2O(l)     arrow        H2SO4(aq)

The reaction is highly exothermic and produces an acid mist
which is difficult to condense into sulfuric acid.


In industry it is easier to dissolve sulfur trioxide
in concentrated (98%) sulfuric acid to form oleum
(oleum is sometimes called fuming sulfuric acid).

This is the balanced chemical equation for the reaction of
sulfur trioxide with sulfuric acid.

sulfur trioxide     +      sulfuric acid        arrow        oleum
        SO3(g)            +          H2SO4(aq)       arrow      H2S2O7(l)

Water is carefully added to oleum to
remake concentrated (98%) sulfuric acid.

This is the balanced chemical equation for the reaction of
oleum with water.

oleum      +       water      arrow    sulfuric acid
 H2S2O7(l)    +      H2O(l)     arrow        2H2SO4(aq)


Sulfuric acid has many uses in industry.


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