How do I make 2M orthophosphoric acid

Special notes for schools
When working with phosphoric acid, protective goggles, protective gloves and protective clothing must be worn. Warm, molten phosphoric acid is almost as aggressive as concentrated sulfuric acid.



Melted, warm phosphoric acid will eat away at kitchen paper.

Movie
properties
Anhydrous orthophosphoric acid forms clear, hard crystals that attract water from the air and have good electrical conductivity. If the crystals are heated above the melting temperature, they melt into a clear liquid. This has a strong oxidizing effect; it destroys paper, for example. The usual phosphoric acid commercially available for laboratory use is an 85% solution in water.



Solution and crystals (without GHS labeling).

Concentrated phosphoric acid is not as strong an acid as concentrated sulfuric acid. The pKa value from the first step of dissociation (H.3PO4) is +2.16. The phosphoric acid dissociates with water in three steps. In the first step, a dihydrogen phosphate anion H is formed2PO4, in the second step a hydrogen phosphate anion HP.O42− and in the third step a phosphate anion PO43−.

First step: H.3PO4 + H2O H2PO4 + H3O+
Second step: H2PO4 + H2O HPO42− + H3O+
Third step: HPO42− + H2O PO43− + H3O+

With the exception of its caustic effect, no dangerous damage to health is to be expected from contact with phosphoric acid, the human body itself contains phosphoric acid and its related compounds. The salts of phosphoric acid, the phosphates, are widespread in nature. Bones contain calcium phosphate, phosphates are important nutrients for the plants in the soil. If you neutralize phosphoric acid with sodium hydroxide solution, sodium dihydrogen phosphate is formed:

H3PO4 + NaOH Close2PO4 + H2O

Manufacturing
use
Phosphoric acid is used to a large extent in the manufacture of fertilizers. In the past, the salts of phosphoric acid, the phosphates, were used as softeners in detergents. Phosphoric acid is also used as a cleaning agent in rust converters or in liquid toilet cleaners, as well as for acidifying soft drinks, for example in Coca Cola. In electronics they are used to etch circuit boards.


Further information and media
The term acid in the household and in chemistry, phosphates