What is "molecularity" of a reaction ? How is it different from the 'order' of a reaction? Name one bimolecular and one trimolecular gaseous reactions.

Explanation

The number of reacting species (atoms, ions or molecules) taking parts in an elementary reaction, which must colloid simultaneously to bring about a chemical reaction is called molecularity of a reaction.
`NH_(4)NO_(2)to N_(2)+ 2H_(2)O` (Unimolecular
`2HI to H_(2)+ I_(2)` (Bimolecular)
`2NO + O_(2)to 2NO_(2)` (Trimolecular)
`to` Molecularity has only integer values `(1,2,3........)`
`to ` It has non zero, non fractio values while order has zero `1,2,3..........` and fractional values.
`to` It is determined by reaction mechanism, order is determined experimentally.