Chapter 19.1, Problem 19.3AFP

Interpretation Introduction

Interpretation:

Preparation of a benzoic acid/benzoate buffer with a $\text{pH}$ of 4.25 has to be given.

Concept Introduction:

Buffer solution:

  An aqueous solution consisting mixture of weak base and its conjugate acid or weak acid and its conjugate base.  Its $\text{pH}$ value changes very small when a small amount of strong base or an acid added to it.

Buffer capacity:

A quantitative measure of the resistance of a buffer solution to pH value change on the addition of hydrogen ion or hydroxide ion is known as buffer capacity.

$\text{Buffering}\text{capacity}\text{=}\frac{\text{sum}\text{additions}\text{of}\text{acid}\text{or}\text{base}}{\text{change}\text{in}\text{pH}\text{value}}$

If u have two or more buffer solutions, then slowly add acid to the each of the solutions and see how much the pH value changes with each addition of acid for each solution.  The solution which has the least amount of change in pH value is the best buffer solution and has the highest buffering capacity.

If a buffer has high capacity then it has a great resistance to $\text{pH}$ change.  When the concentration of weak acid and weak base are high, we get a buffer with high capacity.