Order of reaction : The number of reactiong species (atoms, ions or molecules) taking parts in an elementry reaction, which must collion, simultaneously to bring about a chemical reaction is called molecularity of a reaction
`NH_(4)NO_(2)to N_(2)+ I_(2)` (Unimilecular)
`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 fraction values while order has zero, `1,2,3........` and ractional values.
`to` It is determined by reaction mechanism, order is determined experimentally.
