Question

Explain the following:

BF₃ does not hydrolyse.

Answer 1

Unlike other boron halides, BF₃ does not hydrolyse completely. Instead, it hydrolyses incompletely to form boric acid and fluoroboric acid. This is because the HF first formed reacts with H₃BO₃.

   \[\ce{BF3 + 3H2O -> H3BO3 + 3HF] × 4}\]

\[\ce{H3BO3 + 4HF -> H^{+} + [BF4]^{-} + 3H2O] × 3}\]
                                                                                    

\[\ce{4BF3 + 3H2O -> H3BO3 + 3[BF4]^{-} + 3H+}\]