Question

The catalyst used in the contact process is:
A.\[\text{A}{{\text{l}}_{2}}{{\text{O}}_{3}}\]
B. \[\text{C}{{\text{r}}_{2}}{{\text{O}}_{3}}\]
C. \[{{\text{V}}_{2}}{{\text{O}}_{3}}\]
D. \[\text{Mn}{{\text{O}}_{2}}\]

Answer 1

Hint: The preparation of sulphuric on the industrial scale is done by the contact process. The use of catalysts plays an important role in the contact process. The catalyst used is an oxide of the element with the atomic no. of 23.

Complete answer:
-In the given question, we have to identify the catalyst that is used in the preparation of sulphuric acid by the contact process.
- As we know that contact process is the production of the sulphuric acid for industrial purposes.
- There are mainly three steps involved in the contact process i.e.
1. Production of sulphur dioxide: The process is carried out by burning the powdered sulphur.
- \[{{\text{S}}_{8}}\text{ + 8}{{\text{O}}_{2}}\text{ }\to \text{ 8S}{{\text{O}}_{2}}\]
2. Oxidation of sulphur dioxide: This is a key step because here the production of sulphur trioxide takes place by the oxidation process under certain conditions such as the temperature is 673-723 K, pressure of 1.5 - 2 bar, excess of oxygen is used.
- At this process, the catalyst is also used that is vanadium pentoxide so that the reaction moves towards the equilibrium state fastly.
- To avoid the poisoning of the gas, they must be free from the impurities of arsenic oxide and dust particles.
$\text{2S}{{\text{O}}_{2}}\text{ + }{{\text{O}}_{2}}\text{ }\to \text{ 2S}{{\text{O}}_{3}}$
3. Conversion of sulphur trioxide into sulphuric acid: $\text{S}{{\text{O}}_{3}}$ is absorbed in conc. sulphuric acid to get oleum.
$\text{S}{{\text{O}}_{3}}\text{ + }{{\text{H}}_{2}}\text{S}{{\text{O}}_{4}}\text{ }\to \text{ }{{\text{H}}_{2}}{{\text{S}}_{2}}{{\text{O}}_{7}}$
- Now, the oleum is diluted to get more quantity of ${{\text{H}}_{2}}\text{S}{{\text{O}}_{4}}$ i.e.
${{\text{H}}_{2}}{{\text{S}}_{2}}{{\text{O}}_{7}}\text{ }\text{+ }{{\text{H}}_{2}}\text{O }\to \text{ 2}{{\text{H}}_{2}}\text{S}{{\text{O}}_{4}}$

Therefore, option C is the correct answer.

Note:
The plants used in which the contact process consist of the sulphur burner in which $\text{S}{{\text{O}}_{3}}$ is produced, a purification unit in which the dust, arsenic oxide impurities are removed, catalyst converter and absorption tower.