Abstract

Buffer solutions were prepared and their pH measured to determine their buffering capacity. Three buffer solutions were utilized; an undiluted buffer, a diluted buffer solution with 10ml water and a diluted buffer solution with 18ml water. In the undiluted buffer solution there was minimal pH change with a high of 6.78 and a low of 6.47. In the buffer solution in which 10ml of water was added there was minimal pH change with a high of 6.78 and a low of 6.23. In the buffer solution in which 18ml water was added there was significant change in pH with a high of 6.1 and a low of 2.27.

Introduction

A buffer solution is a solution that is made up of water and a chemical which gives it unique properties with regard to its pH. The chemical is referred to as buffer agent. The buffer agent resists changes in pH when exposed to bases and acids. The aforementioned property makes it useful in dealing with various chemical accidents, protecting sensitive equipment and balancing internal processes of a number of living things.

A buffer agent dissolved in water makes a buffer solution. It is constituted of (HA) an acid and a conjugate base (A-) mixed in water. Once there exists a chemical balance between HA and A- the addition of any bases or acids will be neutralized. This will result in little pH change of the solution. An increase in HA and A- as a result of the addition of bases or acids decreases the buffering capacity of the solution. This implies that the solution acts as a buffer up to a certain point when it is no longer viable.

Hydrolysis equation relating a buffer agent:

HA (aq) + H2O(l) - H2O+ (aq) + A-(aq)

The acid dissociation constant can therefore be written as:

K=[H2O+][A-]/HA (1)

Rearranging the equation gives:

[H2O+]=Ka [HA]/[A-] (2)

Since pH is given to a good approximation by

pH= -log10[H2O+] (3)

taking