In Lewis acid–base theory, which statement is correct?

In Lewis acid–base theory, which statement is correct?

• A. A Lewis acid donates an electron pair; a Lewis base accepts an electron pair.
• B. A Lewis acid dissociates to yield H+.
• C. A Lewis acid accepts an electron pair; a Lewis base donates an electron pair.
• D. A Lewis base increases the pH of a solution.

Answer: (C)

In Lewis acid–base theory, a Lewis base donates an electron pair and a Lewis acid accepts an electron pair. The statement that matches this is that a Lewis acid accepts an electron pair; a Lewis base donates an electron pair. This describes the fundamental interaction: a donor with a lone pair (the base) forms a bond with an acceptor that has an empty orbital (the acid), creating a Lewis adduct or coordinate bond. A classic example is ammonia donating its lone pair to boron in boron trifluoride, forming a stable complex. The other ideas come from different chemical theories. Saying the acid dissociates to yield H+ reflects Arrhenius or Bronsted–Lowry concepts, not the electron-pair transfer central to Lewis theory. And noting that a Lewis base raises the pH of a solution ties basicity to solution properties, which isn’t the defining Lewis interaction, since the same base can act as a Lewis donor without guaranteeing a pH change in every solvent or condition.

In Lewis acid–base theory, a Lewis base donates an electron pair and a Lewis acid accepts an electron pair. The statement that matches this is that a Lewis acid accepts an electron pair; a Lewis base donates an electron pair. This describes the fundamental interaction: a donor with a lone pair (the base) forms a bond with an acceptor that has an empty orbital (the acid), creating a Lewis adduct or coordinate bond. A classic example is ammonia donating its lone pair to boron in boron trifluoride, forming a stable complex.

The other ideas come from different chemical theories. Saying the acid dissociates to yield H+ reflects Arrhenius or Bronsted–Lowry concepts, not the electron-pair transfer central to Lewis theory. And noting that a Lewis base raises the pH of a solution ties basicity to solution properties, which isn’t the defining Lewis interaction, since the same base can act as a Lewis donor without guaranteeing a pH change in every solvent or condition.