Read the passage carefully and answer the questions.
The transition metals and their compounds are known for their catalytic activity. This activity is ascribed to their ability to adopt multiple oxidation states and to form complexes. Vanadium(V) oxide (in Contact Process), finely divided iron, and nickel (in Catalytic Hydrogenation) are some of the examples. Catalysts at a solid surface involve the formation of bonds between reactant molecules and atoms of the surface of the catalyst (first row transition metals utilise 3d and 4s electrons for bonding). This has the effect of increasing the concentration of the reactants at the catalyst surface and also weakening of the bonds in the reacting molecules (the activation energy is lowering). Also because the transition metal ions can change their oxidation states, they become more effective as catalysts.
Which of the following catalyses the oxidation of \( SO_2 \) in the manufacture of sulphuric acid?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Vanadium(V) oxide
In the Contact process for sulphuric acid, sulphur dioxide is oxidised to sulphur trioxide by air. The reaction is slow on its own and is run over vanadium(V) oxide, \( \ce{V2O5} \):
\( \displaystyle \ce{2SO2(g) + O2(g)} \xrightarrow{\ce{V2O5}} \ce{2SO3(g)} \)
The sulphur trioxide is then absorbed in sulphuric acid to give oleum, which is diluted to the acid. Vanadium works here because it moves easily between the +5 and +4 oxidation states: \( \ce{V2O5} \) oxidises \( \ce{SO2} \) and is itself re-oxidised by oxygen.
NCERT (2026-27 edition):
Some Applications of d- and f-Block Elements – “… Many of the metals and/or their compounds are essential catalysts in the chemical industry. V2O5 catalyses the oxidation of SO2 in the manufacture of sulphuric acid. TiCl4 with Al(CH3)3 forms the basis of the Ziegler catalysts used to manufacture polyethylene (polythene). Iron catalysts are used in the Haber process for the production of ammonia from N2/H2 mixtures. Nickel catalysts enable the hydrogenation of fats to proceed. In the Wacker process the oxidation of ethyne to ethanal is catalysed by PdCl2.”