Chapter 18, Problem 18.135P

(a)

Interpretation Introduction

Interpretation:

A weak Bronsted-Lowry base is necessarily a weak Lewis base or not has to be explained with an example.

Concept Introduction:

Bronsted-Lowry base:

Any species that has the capability of accepting a proton, which requires a lone pair of electrons to bond to ${\text{H}}^{\text{+}}$ is said to be Bronsted-Lowry base.

Example:

  ${\text{NH}}_{\text{3(g)}}{\text{+ HCl}}_{\text{(g)}}\to {\text{ NH}}_{\text{4}}{\text{Cl}}_{\text{(s)}}$

In the above reaction, $\text{HCl}$ acts as Bronsted-Lowry acid and donates proton which is accepted by ${\text{NH}}_{\text{3}}$ using its lone pair.  So, ${\text{NH}}_{\text{3}}$ is Bronsted-Lowry base.

Lewis base:

It is an electron-pair donor.  It acts as a nucleophile.  In an acid-base reaction, Lewis base donates electrons to the acid.

Example:

  $\text{A + B }\to \text{ A-B}$

In the above example, A is an acid and B is a base.  B donates electrons to A and forms an adduct.

(b)

Interpretation Introduction

Interpretation:

The Lewis base has to be identified in the given reaction.

  ${\text{Cu(H}}_{\text{2}}{\text{O)}}_{\text{4(aq)}}^{\text{2+}}{\text{ + 4CN}}^{\text{-}}{}_{\text{(aq)}}\rightleftharpoons {\text{Cu(CN)}}_{\text{4(aq)}}^{\text{2-}}{\text{ + 4H}}_{\text{2}}{\text{O}}_{\text{(l)}}$

Concept Introduction:

Lewis base is an electron-pair donor.  It acts as a nucleophile.  In an acid-base reaction, Lewis base donates electrons to the acid.

(c)

Interpretation Introduction

Interpretation:

The given value ${\text{K}}_{\text{c}}\text{ > 1}$ for the reaction.  The stronger Lewis base has to be given in the reaction.

  ${\text{Cu(H}}_{\text{2}}{\text{O)}}_{\text{4(aq)}}^{\text{2+}}{\text{ + 4CN}}^{\text{-}}{}_{\text{(aq)}}\rightleftharpoons {\text{Cu(CN)}}_{\text{4(aq)}}^{\text{2-}}{\text{ + 4H}}_{\text{2}}{\text{O}}_{\text{(l)}}$