Which among the following chemicals is used as catalytic promoter in Haber's process?

$Mo$

The correct answer is Option (4) → $Mo$

In Haber’s process:

• Iron (Fe) acts as the main catalyst

• Molybdenum (Mo) acts as a promoter

Catalyst: Finely divided Iron (Fe) is used to lower the activation energy of the reaction.

Promoter: Molybdenum (Mo) is added in small quantities to enhance the activity and efficiency of the iron catalyst. It acts by increasing the surface area or creating more active sites on the iron for the reactant gases to adsorb 

Option 1: Ni-Nickel is used as catalyst in hydrogenation reactions. Not used in Haber’s process.

Option 2: MnOâ‚‚- Manganese dioxide is used as catalyst in decomposition reactions. Not used in Haber’s process.

Option 3: Fe- Iron is the main catalyst, not the promoter.

Option 4: Mo -Molybdenum acts as a catalytic promoter. It enhances the efficiency of iron catalyst.