In the Bronsted-Lowry definition, an acid is anything which donates H^+ ions in an aqueous solution.
HBr would be considered an acid, because it does dissociate in aqueous solutions in the following dissociation reaction:
HBr(g) rightleftharpoons H^+(aq) + Br^(-)(aq)
Now, a strong acid is an acid which almost completely dissociates in aqueous solutions.
HBr fulfils this, because it very readily dissociates—here's why.
HBr is a hydrohalic acid, or an acid with the formula HX where X is a halogen.
In all hydrohalic acids except for HF, the bond between H and X is very weak because halogens tend to:
- have a high number of energy levels, increasing the size of the halogen. This decreases attraction between H and X.
- Be very electronegative, causing the H-X bond to be very polar.
These two factors cause hydrogen to be very easily "snapped off" of HX, causing it to dissociate into H^+ and X^-.
![CCCBDB listing of experimental data]()
This is also true for HBr—because bromine is so electronegative and large, hydrogen will very easily dissociate from HBr, causing HBr to readily dissociate into H^+ and Br^-.
Dissociation happens so readily that we can say HBr almost completely dissociates, fulfilling the criteria for a strong acid.
