Hydrogen bromide has a boiling point of −66.8 ∘C. It is very soluble in water to give hydrobromic acid; and as with other gases, its solubility decreases with increasing temperature. The conc. HBr(aq) that you use in the lab, i.e. hydrobromic acid, is approx. 48% by weight, and approx. 9⋅mol⋅L−1.