Difference between olementary and nomelementaty reactions:

1. Elementary reactions are single step reactions whereas non-elementary reactions aro multiple step reactions i. e such reactions occur by series of reaction steps.

2. Elamentary reactions are simple in nature whereas the non-elementary reactions are complex in nature.

3. For elementary reaction the order agrees with stoichiometry (i.e order is equal to stoichiometric coefficient of participant) whereas for non-elementary reaction the order does not agrees with stoichiometry (I.e there is difference betwéen order and stoichiometric coefficient).

4. For elementary reaction the order of reaction must have integer value whereas for non-elementary reaction, the order of a reaction may have integer or fractional value.

5. For elementary reaction $2 \mathrm{~A}\rightarrow \mathrm{R}$ , the rate law is $-\mathrm{r}_{\mathrm{A}}=\mathrm{k} \mathrm{C}^2_{\mathrm{A}}$ whereas for non-elementary reaction $2\mathrm {B} \rightarrow \mathrm{S} $ the rate law is $-\mathrm{r}_{\mathrm{B}}=\mathrm{k} \mathrm{C}^n_{\mathrm{B}}$ where n is not equal to 2.

6. Examples of an elementary reaction $ \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}+\mathrm{CH}_{3} \mathrm{COOH} \rightarrow \mathrm{CH}_{3} \mathrm{COOC} \mathrm{H}_{2}+\mathrm{H}_{2} \mathrm{O} $ Examples of non-elementary reaction (i) $\mathrm{H}_{2}+\mathrm{Br}_2 \rightarrow 2 \mathrm{HBr}$ and (ii) $\mathrm{CH}_{3} \mathrm{CHO} \rightarrow \mathrm{CH}_{4}+\mathrm{CO}$