Which of the following is not Lewis acid?

Correct answer: D. Cl-

  • A. HCl
  • B. BF3
  • C. AlCl3
  • D. Cl-

Explanation

The correct answer is Cl-. A Lewis acid is defined as a substance that can accept an electron pair. In this context, Cl- is not a Lewis acid because it already possesses a full octet and is negatively charged, indicating it is more likely to donate an electron pair, thus acting as a Lewis base. On the other hand, HCl can become a Lewis acid when it dissociates, BF3 is electron-deficient and can accept electron pairs, and AlCl3 can also accept electron pairs due to its electron-deficient aluminum center.

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About Acids, Bases and Salts

Acid and base behaviour is explained through the Bronsted-Lowry transfer of protons and the Lewis donation or acceptance of electron pairs. The topic includes pH, pOH, ionisation and water equilibrium, plus salt formation and hydrolysis, where a salt solution may become acidic, basic or neutral.

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