Question

In the CONTACT PROCESS for manufacturing sulphuric acid, the reaction converting \( {SO}_2 \) to \( {SO}_3 \) is

• A. Exothermic and reversible
• B. Endothermic and reversible
• C. Exothermic and irreversible
• D. Endothermic and irreversible

Hint:

Understanding the thermodynamics and kinetics of key industrial reactions like this one is crucial for optimizing reactor design and process economics.

Answer 1

The Correct Option is A

The conversion of sulfur dioxide \( \text{SO}_2 \) to sulfur trioxide \( \text{SO}_3 \) in the Contact Process is a key step in the production of sulfuric acid. This reaction occurs in the presence of a vanadium(V) oxide catalyst.

Step 1: Reaction Characteristics:
The reaction:

\[ 2\ \text{SO}_2 (g) + \text{O}_2 (g) \rightarrow 2\ \text{SO}_3 (g) \]

is known to be exothermic, releasing heat. The standard enthalpy change \( \Delta H^\circ \) for this reaction is negative, indicating that heat is released to the surroundings.

Step 2: Reversibility:
This reaction is also reversible. Under industrial conditions, it does not go to completion, and the formation of \( \text{SO}_3 \) can be reversed back to \( \text{SO}_2 \) and \( \text{O}_2 \) under certain conditions. The use of a catalyst and optimized conditions such as temperature and pressure help shift the equilibrium towards the formation of more \( \text{SO}_3 \).

Step 3: Industrial Significance:
The exothermic nature of the reaction helps in maintaining operational efficiency, while its reversibility is critical for maximizing \( \text{SO}_3 \) yield through the recirculation of unreacted gases and careful control of reaction conditions.