Question
Write a note on molecularity of a reaction and its different types.
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Answer
→ Molecularity of a reaction: 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 molecularit of a reaction.
→ For elementary reaction, order of a reaction an molecularity of a reaction are same.
→ The reaction can be unimolecular when on reacting species is involved. For exampl decomposition of ammonium nitrite.
$NH _4 NO _2 \rightarrow N _2+2 H _2 O$
→ Bimolecular reactions involve simultaneous collision between two species, for example, dissociation of hydrogen iodide. $2 HI \rightarrow H _2+ I _2$
→ Trimolecular or tetramolecular reactions involve simultaneous collision between three reacting species, for example, $2 NO + O _2 \rightarrow 2 NO _2$
→ The probability that more than three molecules can collide and react simultaneously is very small. Hence, the reaction with the molecularity three are very rare and slow to proceed.
→ For elementary reaction, order of a reaction an molecularity of a reaction are same.
→ The reaction can be unimolecular when on reacting species is involved. For exampl decomposition of ammonium nitrite.
$NH _4 NO _2 \rightarrow N _2+2 H _2 O$
→ Bimolecular reactions involve simultaneous collision between two species, for example, dissociation of hydrogen iodide. $2 HI \rightarrow H _2+ I _2$
→ Trimolecular or tetramolecular reactions involve simultaneous collision between three reacting species, for example, $2 NO + O _2 \rightarrow 2 NO _2$
→ The probability that more than three molecules can collide and react simultaneously is very small. Hence, the reaction with the molecularity three are very rare and slow to proceed.
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