Q.In Haber's process, hydrogen is obtained by reacting methane with steam in presence of NiO as catalyst. The process is known as steam reforming. Why is it necessary to remove CO when ammonia is obtained by Haber's process?

A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change, and catalysis is the phenomenon. A catalyst provides an alternative path of lower activation energy.

Two important characteristics of solid catalysts:

• Activity — the ability to speed up a reaction. It depends on the strength of chemisorption; the reactants must be adsorbed strongly enough to react but not so strongly that products cannot leave.
• Selectivity — the ability to direct a reaction to yield a particular product (e.g. the same reactants give different products with different catalysts). A catalyst is highly specific in its action. …