Give examples of zero order reactions.

(N/A) Zero order reactions are relatively uncommon but they occur under special conditions.
Some enzyme-catalyzed reactions and reactions occurring on metal surfaces are examples of zero order reactions.
Example $1$: The decomposition of gaseous ammonia on a hot platinum surface is a zero order reaction at high pressure.
$2 NH_{3(g)} \xrightarrow{1130 \ K, Pt \text{ catalyst}} N_{2(g)} + 3 H_{2(g)}$
$Rate = k[NH_3]^0 = k$
In this reaction,platinum metal acts as a catalyst. At high pressure,the metal surface gets saturated with gas molecules. Therefore,further changes in concentration do not alter the amount of ammonia on the surface of the catalyst,making the rate of the reaction independent of its concentration.
Example $2$: The thermal decomposition of $HI$ on a gold surface is another example of a zero order reaction.