Phenol (C6 H5 OH,. also called carbolic acid ) has a p Ka of 9.89. It is used to preserve body t

step 1 In this question, we're going to be looking at the ionization process of C6 H5 in H2O to produce

Phenol (C6 H5 OH,. also called carbolic acid ) has a p Ka of...

Phenol $\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH},\right.$ also called carbolic acid $)$ has a $\mathrm{p} K_{\mathrm{a}}$ of 9.89. It is used to preserve body tissues and is quite toxic. Calculate the fraction of the acid ionized in $0.010 \mathrm{M}$ and $0.0010 M$ phenol.

Key Concepts

Acid Dissociation Constant (Ka) and pKa

The acid dissociation constant (Ka) quantifies the extent to which an acid donates protons in solution, indicating its strength as an acid. The pKa, a logarithmic measure of the Ka, is used because it conveniently scales the wide range of possible Ka values. A lower pKa value corresponds to a stronger acid, whereas a higher pKa indicates a weaker acid. Understanding pKa is essential in predicting the position of equilibrium in acid-base reactions and determining the proportion of acid that exists in its ionized form under given conditions.

Fraction Ionized (Degree of Ionization)

The fraction ionized, or degree of ionization, describes the ratio of the concentration of the ionized form of an acid to the total concentration of the acid in solution. For weak acids, this fraction is often much less than one and depends on both the acid’s dissociation constant (Ka or pKa) and the solution’s concentration and pH. This concept is important for understanding how much of an acid will contribute to the acidity of a solution and is critical in various biochemical and industrial processes.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation provides a convenient way to relate the pH of a solution to the pKa of an acid and the ratio of the concentration of its conjugate base to the undissociated acid. This equation is especially useful for calculating the fraction ionized in weak acid systems, as it simplifies the determination of equilibrium concentrations in buffers and other biological and chemical systems. Its use is fundamental in predicting the behavior of acid-base equilibria in various contexts.

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