Chapter 16, Problem 110IL

(a)

Interpretation Introduction

Interpretation:

The trend in acid strength has to be explained.

Concept Introduction:

A carboxylic acid can behave as a stronger bronsted acids when the hydrogen atom of alpha carbon is replaced by an anion. This condition is enhanced by:

($1$) The presence of electronegative atom.

($2$) The Greater positive formal charge on the central atom.

($3$) The Possibility of resonating structures for the anion that delocalize the negative charge on the anion, which lead to stability.

(b)

Interpretation Introduction

Interpretation:

The trend in acid strength and the acid which have the highest $\text{pH}$ and which have the lowest $\text{pH}$ is to be stated.

Concept Introduction:

The $\text{pH}$ is a measure of Hydronium ion concentration. The expression for $\text{pH}$ is,

$\text{pH}=-\text{log}\left[{\text{H}}_3{\text{O}}^{\text{+}}\right]$ (1)

Higher the value of $K_{\text{a}}$, stronger the acid and for the acidic solution $\text{pH}<7$, which means higher the value of $K_{\text{a}}$, smaller the value of $\text{pH}$.