Synthesis database: Hydrobromic acid synthesis

Hydrobromic acid can be synthesized by reacting sulphuric acid with a bromide salt. In this case, sodium bromide has been used, which is shown in the following chemical equation:

H₂SO₄ + NaBr -> NaHSO₄ + HBr

Along with sodium bromide and sulphuric acid, distilled water is also needed. As for the equipment, a distillation apparatus, a heat source, a digital scale, a measuring cylinder, a thermometer and a pipette have also been prepared.

First, 103 grams of sodium bromide were dissolved in 150 grams of distilled water. To this solution, 164 grams of concentrated sulphuric acid have slowly been added.

The addition of sulphuric acid was done gradually. Nevertheless, a small amount of bromide ions has been oxidized, thereby forming elemental bromine which gave the solution an orange color.

After all the acid has been added, the solution was left to cool down to room temperature. During that time, crystals of sodium bisulphate formed. These crystals were removed by filtration and the remaining solution was distilled.

This way, 164 grams of hydrobromic acid solution have been obtained. The mass fraction of hydrobromic acid in the solution was approximately 37%. The obtained solution had a yellow coloration due to small amounts of elemental bromine which was also present. If that presents a problem, the distillate can be collected only after it becomes clear (the bromine leaves the solution first due to the lowest boiling point). If one wants to prepare highly concentrated acid, it is important to collect only the fraction which distills over at approximately 122 °C (the boiling point of the azeotropic mixture of water and hydrobromic acid, in which the mass fraction of HBr equals approximately 48%).