Formula of Hydrogen sulphide: H2SRelative Molecular Mass: 34
Vapour Density: 17
Preparation of hydrogen sulphideHydrogen sulphide is prepared by the action of sulphuric acid on metal sulphides.
It is collected by the upward displacement of air.
Chemical properties of hydrogen sulphide
Hydrogen sulphide turns wet blue litmus paper red. It is a weak dibasic acid.
It is a combustible gas, and burns with a blue flame. In a limited supply of oxygen or air, the products are water and sulphur. In excess of air or oxygen, the products are water and sulphur dioxide.
Hydrogen sulphide acts as a powerful reducing agent.
a) With concentrated sulphuric acid
When passed through concentrated sulphuric acid, it reduces the acid to sulphur.
b) With sulphur dioxide
Hydrogen sulphide reduces sulphur dioxide to sulphur.
Precipitation of Sulphides
When hydrogen sulphide is passed through aqueous solutions of metallic salts, the sulphides of the respective metals get precipitated. These sulphides have characteristic colours.
2. Hydrogen sulphide is used in the preparation of metallic sulphides.