Rusting of iron is the example of _ reaction:

Explanation

Rusting of iron is a slow process because it involves the reaction of iron with oxygen and water to form iron oxide (rust). This reaction occurs at the surface of the iron, where iron atoms react with oxygen molecules and water molecules to produce rust. The process is slow due to the relatively low reactivity of iron in normal atmospheric conditions. Additionally, the formation of a stable layer of rust on the surface of the iron acts as a barrier, slowing down further reaction with oxygen and water. The slow rate of reaction and the protective layer of rust make rusting of iron a gradual and slow process.