Experiment to demonstrate the effects of buffers on ph changes.

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1.0 Title: Buffer and pH changes

2.0 Abstract:

In the beginning, processes are affected by the hydrogen ion concentration and the control of pH is important in organisms and their cells because chemical reactions like for an example, the ambient pH affects the enzyme function. However, some side chains of amino acids (R-groups) have ionizable groups like carboxyl or amine groups but changes in pH can alter the number of positively and negatively charged groups. Furthermore, the net charge on the protein effects its three-dimensional structure and thus causing it to have an enzymatic activity. Also, when working with living systems in a laboratory it is necessary to pay close attention to the pH of solutions for that same reasons. Moreover, chemicals that tend to prevent changes in the concentration of hydrogen ions are buffers which are chemicals or combinations. In the lab, we will learn about some buffered solutions to gain a further understanding of how buffers work and to observe the range of buffering capacity. When analysing the data, will make use of graphs and see the relationship of pH to pKa using the Henderson-Hasselbalch equation. In general, buffers are composed of mixtures of weak acids and their corresponding salts and by using the Lowry Bronstead definition, an acid is a compound that can donate a hydrogen ion. However, a weak acid is one that does not completely dissociate or ionize, in a solution.

3.0 Introduction:


Mainly, the purpose of this lab is to demonstrate the power and importance of buffer sin regulating the pH of solutions, by adding very small amounts of acid or base to  different buffer solutions. Students were able to calculate the buffer capacities of those solutions and some general trends with regard to buffer strength with regards to acid/base balance. Furthermore, the buffer capacity β, is important in evaluating the buffers used in the lab. The buffer capacity is calculated  using the equation below: -

In this equation β represent that the buffer capacity, d[b] and d[a] are very small change in the concentration of a strong base or acid respectively, and dpH represents the very small change in pH resulting from the addition of strong acid or base. However, by understanding buffer capacity which is important because it allows chemists to determine whether or not a given buffer is suitable for an application.

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The objective of this lab was to learn how to measure the pH using the correct tools and procedures. Preparing a buffer from acetic acid and sodium acetate. Testing the ability of buffered and unbuffered solutions to resist pH changes when strong acids and bases are added

4.0 Materials and Methods:


Beakers, distilled water, sodium chloride, solid sodium acetate, acetic acid, stirring rod, hydrochloric acid, pipette, pH meter, magnetic stirrer, spin bar, sodium hydroxide


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