Calculate the percentage ionization of acetic acid in...

Calculate the percentage ionization of acetic acid in solutions having concentrations of $1.0 \mathrm{M}, 0.10 \mathrm{M}$, and $0.010 \mathrm{M}$. How does the percentage ionization of a weak acid change as the acid becomes more dilute?

Key Concepts

Weak Acid Ionization

Weak acids, unlike strong acids, do not completely dissociate in solution; only a small fraction of the acid molecules ionize to produce hydrogen ions and its conjugate base. This incomplete ionization is due to the equilibrium established between the non-ionized acid and its ions.

Acid Dissociation Constant (Ka)

The acid dissociation constant (Ka) is a quantitative measure of the strength of a weak acid. It represents the equilibrium constant for the ionization reaction, where a higher Ka value indicates a greater degree of ionization. This constant is intrinsic to the acid and remains the same independent of the acid’s concentration.

Percentage Ionization

Percentage ionization is the ratio of the concentration of ionized acid to the initial concentration of the acid, expressed as a percentage. It provides insight into the extent of ionization in the solution, with lower percentages indicating that only a small fraction of the acid molecules are ionized.

Effect of Dilution on Ionization

When a solution of a weak acid is diluted, the concentration of the non-ionized acid decreases, causing an increase in the percentage ionization. This occur because the equilibrium shifts to favor the production of more ions (as predicted by Le Chatelier’s principle) even though the acid's intrinsic strength (Ka) remains unchanged.

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