Answer: Vanadium(V) oxide (V 2 O 5 ).
- A Vanadium(V) oxide (V<sub>2</sub>O<sub>5</sub>)
- B Iron, the catalyst used instead in the Haber process for ammonia
- C Platinum, the catalyst used instead in the Ostwald process for nitric acid
- D Nickel, the catalyst used instead in the hydrogenation of vegetable oils
Correct answer: A. Vanadium(V) oxide (V<sub>2</sub>O<sub>5</sub>)
Explanation: V<sub>2</sub>O<sub>5</sub> catalyses the oxidation of SO<sub>2</sub> to SO<sub>3</sub> in the Contact process for H<sub>2</sub>SO<sub>4</sub> manufacture.
Aqueous solutions of transition metal ions show characteristic colours caused by electrons absorbing visible light to jump between split d-orbitals; the exact colour depends on the metal, its oxidation state, and surrounding ligands.
Concept context
Transition metals (d-block) and lanthanides/actinides (f-block). Known for coloured compounds, variable oxidation states, complex formation, and catalytic properties. Frequently tested in JEE and NEET.