When silver chloride (AgCl) is exposed to sunlight, it undergoes a color change from white to purple or grey. This is due to a photochemical reaction known as photodecomposition.

Here's the breakdown:

* Photodecomposition: This is a chemical reaction initiated by light. In this case, sunlight provides the energy needed for the reaction.

* Reaction: Sunlight causes silver chloride to decompose into metallic silver (Ag) and chlorine gas (Cl₂):

* 2AgCl (s) → 2Ag (s) + Cl₂ (g)

* Color Change: The formation of metallic silver, which is grey, is responsible for the color change.

Key Points:

* This is a decomposition reaction, where a single compound breaks down into simpler substances.

* The reaction is endothermic, meaning it absorbs energy from the sunlight.

* Silver chloride is used in photographic film because of its sensitivity to light. The silver particles formed upon exposure are what create the image.