Question 18.15: Identifying Lewis Acids and Bases Problem Identify the Lewis......

Plan We examine the formulas to see which species accepts the electron pair (Lewis acid) and which donates it (Lewis base) in forming the adduct. The Lewis base must have a lone pair of electrons.

Solution (a) The $H^+$ ion accepts an electron pair from the $OH^−$ ion in forming a bond. $H^+$ is the Lewis acid and $OH^−$ is the Lewis base.

(b) The $Cl^−$ ion has four lone pairs and uses one to form a new bond to the central B. $BCl_3$ is the Lewis acid and $Cl^−$ is the Lewis base.

(c) The $K^+$ ion does not have any valence electrons to provide, so the bond is formed when electron pairs from O atoms of water enter empty orbitals on $K^+$.
$K^+$ is the Lewis acid and $H_2O$ is the Lewis base.

Check The Lewis acids ($H^+ ,  BCl_3,$ and $K^+$) each have an unfilled valence shell that can accept an electron pair from the Lewis base ($OH^−,  Cl^−,$ or $H_2O$).