Question

The purpose of the Contact process is to:
A. Manufacture sulphuric acid
B. Manufacture nitric acid
C. Manufacture hydrochloric acid
D. Manufacture sulphonic acid

Answer 1

Hint: In the Contact process, oleum is prepared, and then it is diluted to form the final product.

Complete answer:
The purpose of the Contact process is to manufacture sulphuric acid. The Contact process is used in large scale preparation of sulphuric acid in the industries. Let us know more about the steps involved in the contact process.
In the very first step, sulphur dioxide is prepared by heating sulphur in excess air.
${ S }_{ \left( s \right) }+{ { O }_{ 2 } }_{ \left( g \right) }\longrightarrow S{ { O }_{ 2 } }_{ \left( g \right) }$
Since excess oxygen is used in the first step, the unused oxygen is passed on for the second step. In this step, the sulphur dioxide formed is converted into sulphur trioxide. This reaction is a reversible reaction so Vanadium pentoxide is used as a catalyst to gain the maximum output in the forward direction. This catalyst favours the forward reaction to the backward reaction.
${ S }{ { O }_{ 2 } }_{ \left( g \right) }+{ { O }_{ 2 } }_{ \left( g \right) }\overset { { V }_{ 2 }{ O }_{ 5 } }{ \rightleftharpoons } S{ { O }_{ 3 } }_{ \left( g \right) }$
In the third step, the sulphur trioxide produced in the last step is dissolved in concentrated sulphuric acid to produce Oleum. Oleum is known by two names: Fuming sulphuric acid and disulphuric acid. As the name suggests, it has two sulphuric acid molecules bound together. The formula of oleum is ${ H }_{ 2 }{ S }_{ 2 }{ O }_{ 7 }$. It is further diluted with water to form sulphuric acid as the final product.
$S{ { O }_{ 3 } }_{ \left( g \right) }+{ H }_{ 2 }{ { SO }_{ 4 } }_{ \left( l \right) }\longrightarrow { H }_{ 2 }{ S }_{ 2 }{ { O }_{ 7 } }_{ \left( l \right) }$
${ H }_{ 2 }{ S }_{ 2 }{ { O }_{ 7 } }_{ \left( l \right) }+{ H }_{ 2 }{ O }_{ \left( l \right) }{ \longrightarrow H }_{ 2 }{ { SO }_{ 4 } }_{ \left( l \right) }$

Note: Don’t confuse sulphuric acid with sulphonic acid. Sulphonic acid belongs to the class of organosulfur compounds. The general formula of sulphonic acid is $R-{ S\left( =O \right) }_{ 2 }-OH$, where R is any organic aryl or alkyl group.