Final answer:
Adding different substances to an a) acetic acid-sodium acetate buffer affects concentrations of acetic acid, hydronium ion, and acetate ion in characteristic ways that illustrate the buffer's capacity to resist changes in pH and maintain hydronium ion concentration.
Step-by-step explanation:
Effects of Adding Substances to an Acetic Acid-Sodium Acetate Buffer
When various substances are added to an acidic buffer solution of equal concentrations of acetic acid and sodium acetate, the following effects occur on the concentrations of acetic acid, hydronium ion, and acetate ion:
- Acetic acid: Adding more acetic acid increases the concentration of acetic acid, without significantly altering the concentrations of hydronium ion and acetate ion, due to the buffer action.
- Sodium hydroxide (NaOH): The addition of NaOH will cause the hydroxide ions to react with the hydronium ions to form water. This will decrease the concentration of hydronium ions and increase the concentration of acetate ions as more acetic acid dissociates to restore equilibrium.
- Hydrochloric acid (HCl): Adding HCl will increase the concentration of hydronium ions as they combine with acetate to form more acetic acid, reducing acetate ion concentration slightly.
- Sodium acetate: The addition of sodium acetate will increase the concentration of acetate ions and slightly decrease the concentration of hydronium ions as the reaction shifts to maintain equilibrium.
These changes showcase the characteristic action of a buffer solution to resist changes in pH upon the addition of small amounts of strong acids or bases, maintaining a relatively constant hydronium ion concentration.