Chapter 20.SE, Problem 42AP

Interpretation Introduction

Interpretation:

The difference between the first and second ionization constants of dibasic acids decreases with increase in distance between the carboxyl groups, as shown in the table, is to be explained.

Concept introduction:

The carboxylate ion obtained by first ionization has one negative charge while the dicarboxylate anion obtained by second ionization has two negative charges. If the two negative charges are in close proximity in the anion, the repulsion between the charges makes the formation of the dianion difficult. In that case there will be a large difference between the first and second ionization constants. With increasing distance between the charges, the mutual repulsion decreases, the dianion becomes relatively stable. This results in small differences between first and second ionization constants.

To explain:

Why the difference between the first and second ionization constants of dibasic acids, oxalic, succinic and adipic acids, decreases with increase in distance between the carboxyl groups as shown in the table.