Question

The second step in the production of sulphuric acid(contact process) is given by the equation:

\(2SO_2 (g) + O_2(g) \rightleftharpoons 2SO_3(g)\)

Ideally, which conditions would increase the yield of this reaction?

• A. High temperature, high pressure
• B. Low temperature, low pressure
• C. Low temperature, high pressure
• D. High temperature, low pressure

Answer 1

The correct option is C

Low temperature, high pressure

$S{O}_2+O_2\stackrel{V_2{O}_5}{\rightleftharpoons }2S{O}_3+45Kcals$

The given reaction is an exothermic reaction (heat is evolved). In principle (ideally speaking), the yield is decreased at high temperatures. Therefore, in this reaction lower temperatures and higher pressure favour the high yield of SO₃(sulphur trioxide). All this is in accordance with Le Chatelier's principle.