When a white compound 'X' is placed under sunlight it turns grey Give the name of reaction and write the balanced chemical equation?

The reaction that occurs when the white compound 'X' turns grey upon exposure to sunlight is known as photodecomposition or photochemical reaction. A common example of this is the decomposition of silver chloride (AgCl) when exposed to light. The balanced chemical equation for this reaction is:

[ 2 \text{AgCl} (s) \xrightarrow{\text{light}} 2 \text{Ag} (s) + \text{Cl}_2 (g) ]

Here, silver chloride (the white compound) decomposes into elemental silver (the grey product) and chlorine gas.