Which of the metal is used in catalytic hydrogenation?

The correct answer is Option (2) → Ni

In catalytic hydrogenation hydrogen is added across a multiple bond on the surface of a finely divided metal. The metal adsorbs \( \ce{H2} \) and weakens the H–H bond, so the hydrogen atoms add to the C=C bond easily. The usual catalysts are finely divided nickel, palladium and platinum; nickel, being cheap, is the one used industrially, for example to harden vegetable oils into vanaspati ghee:

    \( \displaystyle \ce{R-CH=CH-R' + H2} \xrightarrow[\text{heat}]{\ce{Ni}} \ce{R-CH2-CH2-R'} \)

So the metal used in catalytic hydrogenation is Ni.

Iron, by contrast, is the catalyst of the Haber process (\( \ce{N2 + 3H2 <=> 2NH3} \)), not of hydrogenation.

NCERT (2026-27 edition):
Catalytic Properties – “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 (in Haber’s Process), and nickel (in Catalytic Hydrogenation) are some of the examples.”