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EEJ MAIN Chemistry QUESTION #7153
Question 1
Which of the following pairs consist entirely of compounds that act as Lewis acids?
  • $PH_{3}$ and $SiCl_{4}$
  • $BCl_{3}$ and $AlCl_{3}$✔️
  • $PH_{3}$ and $BCl_{3}$
  • $AlCl_{3}$ and $SiCl_{4}$
Correct Answer Explanation
A Lewis acid is an electron-pair acceptor.
  • $BCl_{3}$ and $AlCl_{3}$ are electron-deficient molecules as the central atoms (B and Al) have only 6 electrons in their valence shell.
  • $PH_{3}$ is a Lewis base due to the lone pair on phosphorus.
  • $SiCl_{4}$ can act as a Lewis acid by expanding its octet, but $BCl_{3}$ and $AlCl_{3}$ are the most classic examples of electron-deficient Lewis acids.