Question

2g of silver chloride is taken in a china dish and the china dish is placed in sunlight for some time. What will be your observation in this case? Write the chemical reaction involved in the form of a balanced chemical equation. Identify the type of chemical reaction.

Answer 1

Hint:Silver chloride consists of a silver cation and a chloride anion. On exposure to sunlight, the compound breaks into its respective elements. The silver metal cation is reduced back to its metal form.

Complete step by step solution:
Silver chloride reacts in the presence of light, or we can say that it is a light sensitive compound. Silver chloride is made up of tightly packed $A{g^ + }$ ions (silver cations) and $C{l^ - }$ ions (chloride anions). Thus, it has the chemical formula $AgCl$.
On exposure to sunlight, the silver chloride compound being light sensitive decomposes into silver and chlorine. Chloride ions undergo oxidation to form bimolecular chlorine gas $C{l_2}$ , releasing two electrons which are taken up by two silver cations which reduce as a result to form elemental silver.
Silver chloride is a crystalline solid and is white in colour and silver metal is grey in colour. So the observation in this case will be conversion of the colour from white colour of silver chloride to grey colour of the metallic silver. The chemical reaction occurring can be written as:
$2AgCl + {\text{light}} \to 2Ag\left( {\text{s}} \right) + C{l_2} \uparrow $

The reaction is a type of photochemical decomposition reaction.

Note:
Decomposition reactions are those reactions in which a compound breaks down or decomposes into two or more other compounds or elements by the action of heat, light, electricity or water.The decomposition reaction occurring in the above given question is known as photochemical decomposition as it is a reaction occurring in the presence of light. The decomposition can also be carried out by the action of heat and electricity and the products obtained are the same.