Why is barium sulfate not soluble in acids



 
 
 
 
 
There are numerous minerals in nature that are composed of sulfates. Sulphates are required for many applications. Plaster of paris is an example of this. It is made up of calcium sulfate dihydrate. Gypsum is used as a building material, and it can be extracted from the mineral of the same name. The mineral gypsum forms beautiful, rod-shaped crystals or transparent platelets, which are known as Marienglas. Plaster of paris occurs in white masses as alabaster plaster of paris. The gypsum crystals contain water molecules that are built into the ion lattice of the salt. When heated, the water of crystallization is released, and plaster of paris is formed. In nature, the anhydrous calcium sulfate occurs as anhydrite. Plaster of paris is used to fill cracks and holes in walls or for plaster of paris for bone fractures. Sulphate minerals also include angelsite, barite, chalcanthite or celestine. Drinking water and mineral water also contain sulfates.
 
 
Chemical properties and manufacture
 
Most sulfates are readily soluble in water. Calcium sulphate is sparingly soluble and barium sulphate and lead sulphate are almost insoluble. In particular, the alkali and alkaline earth sulfates such as potassium sulfate, magnesium sulfate or calcium sulfate are very stable when heated. Hydrogen sulphates such as potassium hydrogen sulphate decompose to disulphates when heated, releasing water, and to sulphates when heated strongly, forming sulfur trioxide. They form an acidic solution with water.

Sulfuric acid + metal Metal sulfate + hydrogen
Sulfuric acid + magnesium Magnesium sulfate + hydrogen
Sulfuric acid + zinc Zinc sulfate + hydrogen
Sulfuric acid + copper no reaction



Diluted sulfuric acid reacts with magnesium and zinc.
 

Sulphates are formed when dilute sulfuric acid reacts with base metals. The corresponding metal salts are formed with the formation of hydrogen. With zinc, for example, you get hydrogen and zinc sulfate, which remains dissolved in the colorless solution. The sulfate anions [SO4]‌2− are chemically detected in analytical chemistry with barium chloride.

 
 
Chemical detection of sulfates
A substance sample or a solution is first acidified with a few drops of hydrochloric acid. If a white precipitate forms after adding barium chloride, sulfate ions are present. White, insoluble barium sulfate precipitates out of the solution.
Detection of sulfate anions:
[SO4]2− + Ba2+ BaSO

 
 
additional Information
 
Worksheet: Analysis of Unknown Substances
sulfuric acid
Sulphate detection in the virtual laboratory
Gypsum as a mineral



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