Chapter 18, Problem 104A

Interpretation Introduction

Interpretation:

The statement is to be critiqued:

A substance whose chemical formula contains a hydroxyl group must be considered to be a base.

Concept introduction:

A substance is considered as a base if it gives hydroxyl ions in an aqueous solution.

Answer to Problem 104A

All substances whose chemical formula contains a hydroxyl group can’t be considered as base.

Only those substances which give hydroxyl ions in aqueous solution are bases.

Explanation of Solution

Let’s take an example:

$\text{N}\text{a}\text{O}\text{H}\text{a}\text{n}\text{d}\text{C}{\text{H}}_3\text{C}\text{O}\text{O}\text{H}$

Both contain hydroxyl groups but $\text{N}\text{a}\text{O}\text{H}$ is a base and $\text{C}{\text{H}}_3\text{C}\text{O}\text{O}\text{H}$ is acid.

Because both ionize as:

$\begin{array}{l}\text{N}\text{a}\text{O}\text{H}\to \text{N}{\text{a}}^{+}+\text{O}{\text{H}}^{-}\end{array}$

  $\begin{array}{c}\text{C}{\text{H}}_3\text{C}\text{O}\text{O}\text{H}\rightleftharpoons \text{C}{\text{H}}_3\text{C}\text{O}{\text{O}}^{-}+{\text{H}}^{+}\end{array}$

Conclusion

Thus, those substances which give hydroxyl ions in aqueous solution are bases.