Question

White silver chloride in sunlight turns to
A. grey
B. yellow
C. green
D. red

Answer 1

Hint: Silver chloride is white in colour and is an ionic crystal. It is held by electrostatic force only. When it is exposed to sunlight, it undergoes dissociation and so changes its colour. Its octahedral structure is broken down and along with it, the colour of the compound fades.

Complete step by step answer:
-Silver chloride is an ionic crystal which is similar to that of NaCl. It has octahedral geometry and the silver ion is attached to 6 chlorine ions in the lattice. It forms a crystal lattice in solid state and is white in colour.
-When sunlight drops on the crystal structure, it leads to the decomposition of the crystal. This is because the lattice energy of the silver chloride molecule is very low. The heat energy of the sun exceeds the overall lattice energy as well as the electron affinity of the silver chloride molecule and this leads to its decomposition.
-The decomposition of silver chloride on exposure to sun can be explained with a chemical reaction which is as follows:
$2AgCl\to 2Ag+C{{l}_{2}}$

-The colour of silver metal is black. But the silver formed from the reaction is in the form of very small particles. The light is not able to reflect properly through these particles and this gives the appearance of the silver particles as grayish colour.
So, the correct answer is “Option A”.

Note: The reaction mentioned above is decomposition reaction. In this, a complex or unstable compound is broken down into 2 or more stable products. Due to this property of silver chloride, it is kept in sealed bottles which are very dark so that sunlight cannot penetrate through them. The light-proof bottles are used for storing silver chloride.