Question

Catalyst used in contact process is:
A. Platinum
B. Ferric oxide + copper oxide
C. Vanadium pentoxide
D. All of the above

Answer 1

Hint: The contact process is the method employed by industries to produce sulphuric acid with a high concentration. In this process oxidation reaction is the main reaction involved which is done by catalyst. The catalyst used is brown yellow solid. It acts as both amphoteric oxide and oxidizing agent.

Complete step by step answer:
The sulphuric acid is a very strong acid which has a very high demand in the industrial sector. It is manufactured in the industries by the help of the contact process.
The contact process is the method applied nowadays to produce sulphuric acid in a high concentration.
The contact process is divided into five steps.
(1) In the first step sulphur combines with oxygen to form sulphur dioxide. The sulphur is melted and combusted with oxygen to give sulphur dioxide.
The reaction is shown below.
$S + {O_2} \to S{O_2}$
(2) In the second step purification of sulphur dioxide takes place in the purification unit.
(3) In the third step catalytic oxidation of sulphur dioxide takes place to form sulphur trioxide. The catalyst used in this process is Vanadium pentoxide ${V_2}{O_5}$.
The reaction is shown below.
$2S{O_2} + {O_2} \to 2S{O_3}$
(4) In the fourth step, sulphur trioxide is converted to oleum.
The reaction is shown below.
\[2S{O_3} + {H_2}S{O_4} \to {H_2}{S_2}{O_7}\]
(5) In the fifth step dilution of ${H_2}{S_2}{O_7}$ to ${H_2}S{O_4}$ takes place.
The reaction is shown below.
${H_2}{S_2}{O_7} + {H_2}O \to 2{H_2}S{O_4}$
Thus, the catalyst used in the contact process is vanadium pentoxide.
Therefore, the correct option is C.

Note:
Don’t get confused between the platinum and vanadium pentoxide as platinum was initially used in the reaction but as it reacts with the arsenic impurities in the sulfur feed stock so vanadium pentoxide is preferred now.