Hydrobromic Acid
Definition and meaning of Hydrobromic Acid in chemistry.
Hydrobromic acid is the aqueous solution formed when hydrogen bromide gas (HBr) dissolves in water, producing a strong acid that ionizes completely into hydronium (H3O+) and bromide (Br-) ions.
In more detail
Because the H-Br bond is longer and weaker than the H-Cl bond, HBr ionizes even more readily than hydrochloric acid, making hydrobromic acid a somewhat stronger acid despite both being fully dissociated (strong) in water. Commercially it is sold as a concentrated aqueous solution, typically around 48% by mass, near the constant-boiling azeotrope that boils at about 124.3 degrees Celsius. It is highly corrosive and is widely used to manufacture inorganic bromide salts and organic bromide compounds, including pharmaceutical intermediates made by adding HBr across alkenes or converting alcohols to alkyl bromides.
Key facts
| Formula | HBr (in water) |
|---|---|
| Field | Inorganic Chemistry |
| Acid strength | Strong acid, pKa approximately -9 |
| Common concentration | About 48% w/w aqueous solution, azeotrope boils at 124.3 C |
Hydrobromic acid reacts with zinc metal to produce zinc bromide and hydrogen gas: Zn(s) + 2 HBr(aq) -> ZnBr2(aq) + H2(g).
Frequently asked questions
Is hydrobromic acid stronger than hydrochloric acid?
Yes. Although both are strong acids that fully ionize in water, the H-Br bond is longer and weaker than the H-Cl bond, so HBr releases its proton more readily, giving hydrobromic acid a lower (more negative) pKa than hydrochloric acid.
What is hydrobromic acid used for?
It is used to produce inorganic bromide salts (such as zinc bromide and calcium bromide) and organic bromide compounds, including alkyl bromides used as intermediates in pharmaceutical and agrochemical synthesis.