Buffer Solutions

Definition

Buffer solutions are aqueous solutions that resist changes in pH upon the addition of small amounts of an acid or base. They maintain a relatively stable pH within a specific range, even when other substances are added that would normally alter the pH of the solution.

5 Must Know Facts For Your Next Test

1. Buffer solutions maintain a relatively stable pH by providing a reserve of hydrogen ions (H+) or hydroxide ions (OH-) to neutralize added acids or bases.
2. The pH of a buffer solution is determined by the pKa of the weak acid or base and the ratio of the concentrations of the conjugate acid-base pair.
3. Hydrolysis of salts in aqueous solutions can create buffer systems, where the salt acts as a weak acid or base and its conjugate counterpart.
4. Polyprotic acids, such as carbonic acid (H2CO3) and phosphoric acid (H3PO4), can form multiple buffer systems within the same solution.
5. Buffer solutions play a crucial role in maintaining the optimal pH for various biological and chemical processes, including enzyme activity, cell function, and analytical techniques.

Review Questions

• Explain how buffer solutions work to maintain a relatively stable pH.
  • Buffer solutions maintain a stable pH by providing a reserve of hydrogen ions (H+) or hydroxide ions (OH-) that can neutralize added acids or bases. The pH of a buffer solution is determined by the pKa of the weak acid or base and the ratio of the concentrations of the conjugate acid-base pair. When an acid or base is added to the buffer, the conjugate acid or base reacts with the added substance, minimizing the change in pH.
• Describe the role of buffer solutions in the hydrolysis of salts and the formation of polyprotic acid buffer systems.
  • Hydrolysis of salts in aqueous solutions can create buffer systems, where the salt acts as a weak acid or base and its conjugate counterpart. For example, the hydrolysis of sodium acetate (CH3COONa) creates a buffer system with acetic acid (CH3COOH) and acetate ion (CH3COO-). Additionally, polyprotic acids, such as carbonic acid (H2CO3) and phosphoric acid (H3PO4), can form multiple buffer systems within the same solution, with each proton dissociation creating a new conjugate acid-base pair.
• Analyze the importance of buffer solutions in maintaining the optimal pH for various biological and chemical processes, and explain how this relates to the concept of coupled equilibria.
  • Buffer solutions play a crucial role in maintaining the optimal pH for various biological and chemical processes, such as enzyme activity, cell function, and analytical techniques. This is because many of these processes are sensitive to changes in pH and require a specific pH range for optimal performance. The concept of coupled equilibria is relevant here, as the buffer system acts as a chemical equilibrium that is coupled to the processes occurring in the solution. The buffer system's ability to resist pH changes allows it to maintain the necessary pH conditions for these coupled equilibria to function properly, ensuring the desired outcomes of the biological or chemical processes.

Related terms

pH:

A measure of the acidity or basicity of a solution, ranging from 0 to 14, with 7 being neutral.

Conjugate Acid-Base Pair: A pair of substances that differ by a single proton, where one is the acid and the other is the base.

Equilibrium Constant (Ka, Kb): The ratio of the concentrations of the products to the reactants at equilibrium, which determines the strength of an acid or base.