Final answer:
A Lewis acid or base is always a Brönsted-Lowry acid or base because the latter's definition covers a broader range of substances. However, it is not necessarily an Arrhenius acid or base, as Arrhenius's definitions are more restrictive.
Step-by-step explanation:
When it comes to acid and base theories, there are a few different definitions in chemistry that classify substances as acids or bases. To answer the question of whether a Lewis acid or base is also an Arrhenius or Brönsted-Lowry acid or base, we must look at the definitions:
- Brönsted-Lowry theory defines an acid as a proton donor and a base as a proton acceptor.
- Arrhenius's theory defines an acid as a substance that increases the concentration of H+ ions when dissolved in water and a base as a substance that increases the concentration of OH- ions.
- The Lewis theory expands on these concepts by defining an acid as an electron-pair acceptor and a base as an electron-pair donor.
Given that all Arrhenius acids and bases are also considered Brönsted-Lowry acids and bases, but not all Brönsted-Lowry acids and bases meet the Arrhenius criteria, the correct choice would be that a Lewis acid or base is not necessarily an Arrhenius acid or base, but it is always a Brönsted-Lowry acid or base. Hence, the answer to the question is b. Brönsted-Lowry.