UPSC NDA II 2024 General Ability Paper

Concept:This is a photochemical decomposition reaction where silver chloride breaks down into silver and chlorine gas when exposed to light.Explanation:The given reaction is:$$2\mathrm{AgCl}(s) \rightarrow 2\mathrm{Ag}(s) + \mathrm{Cl}_2(g)$$Silver chloride is light-sensitive. It absorbs photons from sunlight, which provides energy to break the bonds in $\mathrm{AgCl}$.This decomposition does not happen in the dark, upon simple heating, or under high pressure.When sunlight falls on $\mathrm{AgCl}$, it turns grey due to the formation of metallic silver.The reaction is a classic example of photolysis.Thus, the reaction takes place specifically in sunlight.Answer:Option B: in sunlight.