Question

What is catalyst? Give an example.

Answer 1

Catalyst is a substance that either increases or decreases the rate of a chemical reaction without itself undergoing any chemical change is called a catalyst.
For example, in a reaction known as Haber's process:
$N_2+3H_2\stackrel{\mathrm{Fe}}{\rightleftharpoons }2{\mathrm{NH}}_3+\mathrm{heat}$
Here, iron act as a catalyst and increases the rate of the chemical reaction.