4 Molecularity
of a
Reaction
Another property of a reaction called molecularity helps in
understanding its mechanism The number of reacting species
(atoms, ions or molecules) taking part in an elementary
reaction, which must collide simultaneously in order to bring
about a chemical reaction is called molecularity of a reaction The reaction can be unimolecular when one reacting species is involved,
for example, decomposition of ammonium nitrite Rationalised 2023-24
70
Chemistry
NH4NO2 ® N2 + 2H2O
Bimolecular reactions involve simultaneous collision between two
species, for example, dissociation of hydrogen iodide