Question

Oxidation of Sulphur to Sulphur trioxide is thermodynamically more favourable than oxidation of Sulphur to Sulphur dioxide – true or false?

• A. True
• B. False

Answer 1

The correct option is A True

This is true. In other words, the formation of sulphur trioxide is thermodynamically more favored than that of sulphur dioxide (the heats of formation ${\Delta }_f{H}^{\circ }are370kJ.mo{l}^{-1}$ for sulphur trioxide & $300kJ.mo{l}^{-1}$ for sulphur dioxide respectively). Despite this being the case, the oxidation of Sulphur almost always yields $S{O}_2$ than $S{O}_3$ because the oxidation to the Sulphur trioxide has a significantly higher activation energy. Hence, the pathway from sulphur dioxide to sulphur trioxide is kinetically controlled as:
$2S{O}_2\left(g\right)+O_2\stackrel{Pt,\Delta }{⟶}2S{O}_3\left(g\right)$
In the contact process for the manufacture of Sulphuric acid, $V_2{O}_5$ is the preferred catalyst for the above reaction. Earlier, platinated asbestos was used.