Question

# The catalyst used in the manufacture of sulphuric acid is by contact process ______________. A.$A{{l}_{2}}{{O}_{3}}$B.${{V}_{2}}{{O}_{5}}$C.$C{{r}_{2}}{{O}_{3}}$D.$Mn{{O}_{2}}$

Hint: Contact process is used to manufacture sulphuric acid in high concentrations needed for industrial processes. There are three steps involved in the contact process. Catalyst is a chemical which does not involve in the reaction but fastens the reaction towards the product.

-We know that the contact process is three step processes.
-In the first step Sulphur dioxide is going to prepare from Sulphur.
-In the second step Sulphur dioxide is converted to Sulphur trioxide.
-Without a catalyst it is very difficult to prepare Sulphur trioxide from Sulphur dioxide. There is a need for a catalyst in the preparation of Sulphur trioxide from Sulphur dioxide (second step).
-In the second step addition of an excess amount of oxygen to sulphur dioxide in the presence of the catalyst takes place at higher temperature and pressure in the contact process.
$S{{O}_{2}}+{{O}_{2}}\xrightarrow[{{450}^{o}}C,1-2atm]{Catalyst}S{{O}_{3}}$
-Platinum commonly used to be the catalyst for this reaction in the second step.
-However, platinum is susceptible to reacting with arsenic impurities in the sulfur feedstock.
So, platinum is replaced with vanadium (V) pentoxide (${{V}_{2}}{{O}_{5}}$) in the contact process.
-In the third step Sulphur trioxide is going to convert into sulphuric acid (${{H}_{2}}S{{O}_{4}}$).
-So, the catalyst used in the contact process is vanadium (V) pentoxide (${{V}_{2}}{{O}_{5}}$).

So, the correct option is B.

Note:
Don’t be confused with the words Sulphur dioxide, Sulphur trioxide and Sulphuric acid.
-The molecular formula of Sulphur dioxide is $S{{O}_{2}}$.
-The molecular formula of Sulphur trioxide is $S{{O}_{3}}$.
-The molecular formula of Sulphuric acid is ${{H}_{2}}S{{O}_{4}}$.