Which acid is the strongest?

  • A. Ethanoic acid
  • B. Propanoic acid
  • C. Trichloroethanoic acid
  • D. Butanoic acid

Explanation

Three electronegative chlorine atoms withdraw electron density powerfully and stabilise the carboxylate ion, so trichloroethanoic acid is a strong acid, comparable in strength to some mineral acids. Among the unsubstituted acids, strength falls slightly as the alkyl chain lengthens because alkyl groups release electron density. This is why methanoic acid is the strongest of the simple aliphatic acids.

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