The GATE Grind

GATE 2025 CH – Question 28

Chemical Technology · Inorganic chemical industries · 1 mark · Multiple choice

In the CONTACT PROCESS for manufacturing sulphuric acid, the reaction converting SO$_2$ to SO$_3$ is

  1. Exothermic and reversible
  2. Endothermic and reversible
  3. Exothermic and irreversible
  4. Endothermic and irreversible

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Correct answer: (A) Exothermic and reversible

Explanation

$2SO_2 + O_2 \rightleftharpoons 2SO_3$ releases heat ($\Delta H \approx -98$ kJ/mol) and does not go to completion, so it is exothermic and reversible. That is why the process uses several catalyst beds with cooling between them.