Preparation Buffers

1323 Words Aug 1st, 2013 6 Pages
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
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2.0ml of buffer solution was taken (through the use of a graduated pipette) and 18.0ml of distilled water added to it. The pH of the solution was measured and the buffer capacity tested by the use of the procedure outlined in the previous section.

Results
Discussion and Conclusion

Table 1
There is minimal change in the pH of the buffer with a high of 6.78 and a low of 6.47. The equivalence point is approximately 6.64. This shows that as the quantity of the buffering agent's acid (HA) and conjugate base (A-) changes, the buffering capacity of the solution decreases. As a consequence, a buffer agent can only be utilized up to a given point in which case it does not resist pH changes and seizes to be a buffer solution.

Table 2
There is minimal change in the pH of the buffer with a high of 6.78 and a low of 6.23. The equivalence point is approximately 6.6. The addition of water dissociates the buffer agent further as shown in the equation below:

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

HCl (aq) + H2O(l) - H+(aq) + Cl-(aq)

The concentration of the conjugate base and acid thus changes. The buffering capacity of the solution decreases. As a consequence, a buffer agent can only be utilized up to a given point in which case it does not resist pH changes and seizes to be a buffer solution.

Table 3
There is significant change in the pH of the buffer with a high of 6.10 and a low of 2.27. The equivalence point is approximately 6.1. The addition of water

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