Chapter 4, Problem 39CTQ

Interpretation Introduction

Interpretation: Whether conjugate acid with low $\text{p}{K}_a$ value will donate ${\text{H}}^{+}$ ions more easily than that with high $\text{p}{K}_a$ value is consistent with fact that below acids have $\text{p}{K}_a$ close to zero or not should be determined.

  

Concept introduction: According to the Bronsted-Lowry concept, the substance that donates proton is termed as acid while that accepts or gains protons is called a base. Species formed after loss of protons from acids are known as their respective conjugate bases whereas conjugate acid is produced by the addition of protons to base. The strength of an acid is determined by its $\text{p}{K}_a$ value while that of the base is governed by its $\text{p}{K}_b$ value.

According to Lewis's concept, the substance that donates electron pair is termed as a base while that accepts or gains electron pair is called acid. For example, ${\text{BF}}_{\text{3}}$ is an electron-deficient compound and can easily accept electrons so it is Lewis acid. But ${\text{NH}}_{\text{3}}$ has lone pair of electrons that it can donate easily so it acts as Lewis base.

According to the Arrhenius concept, substances that donate hydrogen ions in solutions are known as acids while bases are substances that release hydroxide ions in solutions.