Question

White silver chloride in sunlight turns to:
(A) grey
(B) yellow
(C) green
(D) red

Answer 1

Hint: Silver chloride upon long exposure to sunlight changes its colour. This is due to the decomposition of silver chloride. Write the chemical reaction for the decomposition of the compound to see the products obtained. Try to identify the colour of the product to answer the question.

Complete step-by-step answer:
A decomposition reaction is a chemical reaction in which a compound breaks down into two or more simple substances. The general form of the reaction is :
$\text{AB }\to \text{ A + B}$
Decomposition reactions, in general, require energy to perform the reaction in the form of heat, light or electricity.
Binary compounds are compounds composed of two elements only. The simplest kind of decomposition reaction is when the binary compounds decompose to give its constituent elements. An example for this is when Mercuric oxide which is a red solid decomposes on heat to produce mercury metal and oxygen gas.
A reaction in which a reactant gives one or more compounds is considered a decomposition reaction. A metal carbonate decomposes into a metal oxide and carbon dioxide in gaseous form. For example, the decomposition of calcium carbonate gives calcium oxide and carbon dioxide as products.
We will now write the reaction of silver chloride in presence of sunlight.
$\text{AgCl }\to \text{ Ag + C}{{\text{l}}_{2\uparrow }}$
The colour of silver chloride changes from white to grey because silver chloride decomposes to give elemental silver which is grey in colour.

Therefore, the correct answer is option (A).

Note: Like silver chloride, silver bromide undergoes the same decomposition reaction giving silver metal and bromine. However, this reaction is very important as it is used in black and white photography. Silver bromide is a light-sensitive material, it helps in the formation of contrast images also called negatives of the picture.