It has been observed that `BF_(3)` does not hydrolyses completely whereas `BCl_(3)` or `BBr_(3)` get easily hydrolysed to form `B(OH)_(3)` and `HX`? Explain.

Explanation

The greater stability of `B-F` bond as compared to `B-Cl` and `B-Br` bonds is due to additional `pi-` bonding in `B-F` bonds of `BF_(3)` molecules.The `B-Cl` and `B-Br` bonds are relatively weak and are easily cleaved by water forming strong `B-OH` bonds instead of stable addition product `(BF_(3).OH_(2))` formed by `BF_(3)`.