Chapter 18, Problem 55A

Interpretation Introduction

Interpretation:

The relationship of the concentrations of hydrogen ions and hydroxyl ions related to the acidic, basic and neutral nature of the solution is to be discussed.

Concept introduction:

According to Arrhenius,

Acid is a substance that gives hydrogen ion and base is a substance that gives hydroxyl ions in aqueous solution.

Answer to Problem 55A

$\text{I}\text{f}\left[{\text{H}}^{+}\right]=\left[\text{O}{\text{H}}^{-}\right]$, the solution is neutral.

$\text{I}\text{f}\left[{\text{H}}^{+}\right]<\left[\text{O}{\text{H}}^{-}\right]$, the solution is basic.

$\text{I}\text{f}\left[{\text{H}}^{+}\right]>\left[\text{O}{\text{H}}^{-}\right]$, the solution is acidic.

Explanation of Solution

In aqueous solution, water is the solvent which is weekly dissociated as,

${\text{H}}_2\text{O}\rightleftharpoons {\text{H}}^{+}+\text{O}{\text{H}}^{-}$

Thus, if the substance is acid, $\left[{\text{H}}^{+}\right]>\left[\text{O}{\text{H}}^{-}\right]$

If the substance is base, $\left[{\text{H}}^{+}\right]<\left[\text{O}{\text{H}}^{-}\right]$

If the substance is neutral, $\left[{\text{H}}^{+}\right]=\left[\text{O}{\text{H}}^{-}\right]$

Conclusion

Thus,

$\text{I}\text{f}\left[{\text{H}}^{+}\right]=\left[\text{O}{\text{H}}^{-}\right]$, the solution is neutral.

$\text{I}\text{f}\left[{\text{H}}^{+}\right]<\left[\text{O}{\text{H}}^{-}\right]$, the solution is basic.

$\text{I}\text{f}\left[{\text{H}}^{+}\right]>\left[\text{O}{\text{H}}^{-}\right]$, the solution is acidic.