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Acids and Alkalis

Manufacture of Sulfuric Acid  -  The Contact Process.

The Effect of using a Catalyst on the Formation of Sulfur Trioxide.

The catalyst for this reaction is Vanadium(V) oxide (V₂O₅).
Transition metals often make good catalysts.

The formation of sulfur trioxide is reversible.

sulfur dioxide + oxygen    sulfur trioxide
2SO_2(g)        +    O_2(g)             2SO_3(g)

We know from reaction rates that a catalyst
can increase the rate of a reaction.

With a reversible reaction, a catalyst will increase the rate
of both the forward and the backward reaction. This
is useful because the catalyst will cause the reaction mixture
to reach its equilibrium composition more quickly.
Note, the catalyst will not change the equilibrium composition.

In the contact process the reactants can be pushed
through the reaction vessel more quickly in the
presence of a catalyst. Without the catalyst the process
would take longer and be more expensive. Compare
this with the formation of ammonia in the Haber process.

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