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

Identifying Lewis Acids and Bases

Problem Identify the Lewis acids and Lewis bases in the following reactions:

(a) H^+  +  OH^− \xrightleftharpoons[]{} H_2O      (b) Cl^−  +  BCl_3  \xrightleftharpoons[]{}  BCl_4^−     (c) K^+  +  6H_2O \xrightleftharpoons[]{}  K(H_2O)_6^+

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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).

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