# The Black Coating On Silver is Due To?

Blacking coating on silver is due to the formation of silver sulphide (Ag2S).

Following is the equation for the formation of silver sulphide:

 $2Ag\;(s)+H_{2}S\;(g)\rightarrow Ag_{2}S\;(s)+H_{2}\;(g)$

## What is Silver Sulphide (Ag2S)?

Silver sulphide is a dense black solid and is insoluble in all solvents but can be degraded by using strong acids. Since it is made of silver and sulfur, it has covalent bonds.

### Chemical Properties of Silver Sulphide

 Chemical formula Ag2S Molecular weight 247.8 Crystal structure Orthogonal Group Silver: 11 and Sulfur: 16

### Mechanical and Thermal Properties of Silver Sulphide

 Density 7.23g/cm3 Melting point 825dC Heat of fusion 56.9J/g Heat of formation -32.6kJ/mol