Which of the following is both an Arrhenius base and Bronsted-Lowry base? a. BF3 b. NaOH c. HNO3 d. NH3
The Correct Answer and Explanation is:
The correct answer is b. NaOH.
Explanation:
Arrhenius Base:
According to the Arrhenius definition, a base is a substance that dissociates in water to produce hydroxide ions (OH⁻).
- NaOH dissociates in water as follows:
NaOH (aq)→Na+(aq)+OH−(aq)\text{NaOH (aq)} \rightarrow \text{Na}^+(aq) + \text{OH}^-(aq)NaOH (aq)→Na+(aq)+OH−(aq)
Since NaOH produces hydroxide ions in water, it is an Arrhenius base.
Bronsted-Lowry Base:
According to the Bronsted-Lowry definition, a base is a substance that accepts a proton (H⁺).
- NaOH in water acts as a Bronsted-Lowry base because the hydroxide ion (OH⁻) can accept a proton (H⁺) from an acid to form water:
OH−(aq)+H+(aq)→H2O\text{OH}^-(aq) + \text{H}^+(aq) \rightarrow \text{H}_2\text{O}OH−(aq)+H+(aq)→H2O
Thus, NaOH is also a Bronsted-Lowry base because it accepts a proton.
Why other options are not correct:
- a. BF3: BF₃ is a Lewis acid, but it does not fit either the Arrhenius or Bronsted-Lowry definition of a base. It does not release OH⁻ or accept H⁺ in solution.
- c. HNO3: HNO₃ is an acid, not a base. It donates protons (H⁺) in solution, making it a Bronsted-Lowry acid and an Arrhenius acid.
- d. NH3: Ammonia (NH₃) is a Bronsted-Lowry base because it can accept a proton to form NH₄⁺. However, it does not produce OH⁻ ions directly from dissociation in water, so it is not an Arrhenius base.
