Silver chloride (AgCl) is a chemical compound that is highly sensitive to light. This sensitivity makes it a classic example of photolytic decomposition in Class 10 Chemistry.
Because AgCl decomposes in the presence of light, laboratory bottles containing silver chloride (and other silver salts like silver nitrate) are always made of dark brown or amber-coloured glass to block light and prevent premature decomposition.
This dramatic colour change from white to grey is a standard textbook observation for chemical reactions.
When white silver chloride is placed in sunlight, it undergoes a photolytic decomposition reaction (decomposition caused by light energy).
The sunlight breaks down the silver chloride into solid silver metal and chlorine gas. The fine particles of silver metal produced are grey in colour, which causes the entire powder to change from white to grey.
Chemical Equation: 2AgCl(s) (White) ---(Sunlight)---> 2Ag(s) (Grey) + Cl₂(g)
Silver bromide behaves in exactly the same way.
Chemical Equation: 2AgBr(s) (Pale Yellow) ---(Sunlight)---> 2Ag(s) (Grey) + Br₂(g)
Because AgCl and AgBr change colour (decompose into dark silver particles) when exposed to light, they were historically used in black-and-white photography. The photographic film was coated with these salts. Wherever light hit the film, it turned dark (grey/black), creating the negative image.
No, Silver Chloride (AgCl) is highly **insoluble in water**. When it is formed in a reaction (like mixing Silver Nitrate and Sodium Chloride), it immediately appears as a thick white solid precipitate.
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