Question

Which substance is an Arrhenius acid? (1) LiF(aq) (3) Mg(OH)2(aq) (2) HBr(aq) (4) CH3CHO

Answer 1

HBr (aq) is an Arrhenius acid.
The equation is HBr(aq) -> H+ + Br- 

Answer 2

Answer: Option (2) is the correct answer.

Explanation:

Arrhenius acid are the species that donate a $H^{+}$ ion or proton.

For example, $HBr \rightarrow H^{+} + Br^{-}$

Whereas LiF, $Mg(OH)_{2}$, and $CH_{3}CHO$ are the substances which do not give a proton upon dissociation. Hence, they are not Arrhenius acids.

Therefore, we can conclude that $HBr(aq)$ substance is an Arrhenius acid.