Buffer Capacity Experiment: Determining the Maximum Buffer Capacity of Acetate Buffers, Exams of Chemistry

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Buffer

Capacity

BCH 312

Experiment (7)

Objectives

n To understand the concept of buffer capacity.

n To determine the maximum buffer capacity of a number of buffer

solutions.

n To establish the relationship between buffer capacity and buffer

concentration.

n Quantitative measure of this resistance to pH changes is called buffer capacity. n Buffer capacity can be defined as the number of moles of H+/OH- ions that must be added to one liter of the buffer in order to decrease /increase the pH by one unit respectively. n Where [H+] = the hydrogen ion concentration of the buffer ,β is the buffer capacity , [C] is buffer concentration. n From the equation that the buffer capacity is directly proportional to the buffer concentration. Buffer Capacity

Method n You are provided with 2 acetate buffers, pH=5. Each with different concentrations ; 0.1 M and 0.2 M. n Transfer 8 ml of each buffer into a 50 ml beaker. n Add 0.5 ml of ( 0.1 M) HCl from the burette and determine the pH of the solution after each addition n Continue adding acid in until pH falls to about 2 pH units from your starting pH. n Plot a Curve of pH versus ml of HCl added and calculate the Buffer capacity n Then compare between two buffer which one has higher buffer capacity and why?