Is HBr a strong acid?

1 Answer
Jun 5, 2018

Yes!

Explanation:

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 dataCCCBDB 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.