In chemistry, the molecular formula HBr is used to represent the aqueous solution hydrobromic acid. The formula indicates that the compound contains one atom of hydrogen, represented by H, and one atom of bromine, represented by Br.
Hydrobromic acid is one of seven strong acids; these are acids with a pKa value that is less than -1.74. The pKa value is related to the value Ka, which is called the acid dissociation constant. Hydrobromic acid has a pKa value of -9, making it one of the strongest strong acids. As a strong acid, HBr completely dissociates one ion when it forms an aqueous solution. That trait means that when HBr is added to water, H2O, it results in a positively charged H3O ion and a negatively charged Br ion.
Hydrobromic acid can be formed by the reaction between dibromine, sulfur dioxide and water. It can also be formed by dissolving the gas hydrogen bromide, also represented by the formula HBr, in water. Hydrobromic acid appears as a pale yellow liquid with an acrid smell. It has a molar mass of 80.91 grams per mole. Hydrobromic acid is often used to produce compounds that contain one or more atoms of bromine.