Which of the following is not a Lewis Acid?

In the context of Lewis acid-base theory, a Lewis acid is a substance that can accept an electron pair, while a Lewis base is a substance that can donate an electron pair.

Analysis of the Options

• a) SiCl₄ (Silicon tetrachloride): SiCl₄ has an empty d-orbital and can accept electron pairs, making it a Lewis acid.
• b) CCl₄ (Carbon tetrachloride): CCl₄ has a complete octet and does not have an empty orbital to accept electron pairs, classifying it as a Lewis base.
• c) H⁺ (Hydrogen ion): H⁺ lacks electrons and can accept electron pairs, making it a Lewis acid.
• d) SnCl₄ (Tin tetrachloride): SnCl₄ has an empty d-orbital and can accept electron pairs, classifying it as a Lewis acid.

Final Answer

The species that is not a Lewis acid is b) CCl₄ (Carbon tetrachloride), as it lacks the ability to accept electron pairs.