HBr is an Arrhenius acid because:
- A it produces hydronium ions in solution.
- B it produces hydroxide ions in solution.
- C it is a polar molecule.
- D it can dissolve in water.
The correct answer and explanation is :
The correct answer is: A) it produces hydronium ions in solution.
Explanation:
An Arrhenius acid is defined as a substance that increases the concentration of H⁺ ions (protons) in an aqueous solution. When we talk about strong acids like HBr (hydrobromic acid), it fits this definition perfectly.
When HBr dissolves in water, it completely ionizes, meaning it breaks apart into ions:
[
\text{HBr} (aq) \rightarrow \text{H}^+ (aq) + \text{Br}^- (aq)
]
However, in real aqueous solutions, free H⁺ ions don’t just float around by themselves. Instead, they quickly attach to water molecules to form hydronium ions (H₃O⁺):
[
\text{H}^+ (aq) + \text{H}_2\text{O} (l) \rightarrow \text{H}_3\text{O}^+ (aq)
]
Thus, when HBr dissolves, it produces a large amount of hydronium ions, making the solution acidic. This behavior — increasing the concentration of hydronium ions — is what defines HBr as an Arrhenius acid.
Now let’s briefly look at the wrong options:
- B) It produces hydroxide ions in solution: Incorrect. Hydroxide ions (OH⁻) are produced by bases, not acids.
- C) It is a polar molecule: While it’s true that HBr is polar, polarity alone doesn’t make something an acid. Many polar molecules (like sugar) are not acids.
- D) It can dissolve in water: Although HBr dissolves easily in water, solubility alone does not define a substance as an acid. Substances like table salt also dissolve in water but are not acids.
Thus, the defining feature of HBr as an Arrhenius acid is that it produces hydronium ions in aqueous solution, making option A the correct answer.