Correct Option
The correct option isBreakdown of ozone
Explanation
Chemical reactions involve the exchange of energy. Reactions that release energy in the form of heat or light are termed exothermic, while reactions that require the absorption of energy (such as heat or electromagnetic radiation) to proceed are termed endothermic or photochemical reactions.
Option Analysis
- Burning of coal Burning of coal: This is a combustion reaction. It is an exothermic process where carbon reacts with oxygen to produce carbon dioxide, releasing a significant amount of energy in the form of heat and light.
- Breakdown of ozone Breakdown of ozone: This is a photochemical reaction (photodissociation). Stratospheric ozone ($O_3$) absorbs high-energy ultraviolet (UV) radiation from the sun. This absorption causes the ozone molecule to split into a dioxygen molecule ($O_2$) and a free oxygen atom ($O$). This process is critical for shielding the Earth from harmful UV rays.
- Rusting of iron Rusting of iron: This is an oxidation reaction. It is an exothermic process that releases heat, although the rate of reaction is slow, making the heat release less perceptible than in combustion.
- Explosion of fireworks Explosion of fireworks: This involves rapid combustion and oxidation reactions. It is highly exothermic, releasing energy in the form of light, heat, and sound.
Key Takeaway: The breakdown of ozone is a photochemical process driven by the absorption of UV radiation, whereas burning, rusting, and explosions are exothermic processes that release energy.