Exp10 - Discussion: This experiment dealt with acid/base...

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Discussion: This experiment dealt with acid/base equilibrium and its uses in buffers and titrations. Buffers work because they are composed of a weak acid and a weak base, which will react with a strong acid or strong base to neutralize it and not alter the pH. If a strong, 1 M base was added to the buffer, the reaction could be described by the equation OH - (aq) + HC 2 H 3 O 2 (aq) H 2 O(l) + C 2 H 3 O 2 in which it can be seen that the base is neutralized by becoming water when reacting with the weak acid so the pH remains unchanged. The first part of the experiment consisted of examining the different methods for constructing buffer solutions from acids and bases. Vinegar, containing 5% acetic acid, and sodium acetate trihydrate were used to create the two buffer solutions. The first one was made by measuring 50 ml of vinegar, adding 3-5 drops of universal indicator and adding the required amount of sodium acetate trihydrate needed to make a pH of buffer 5. The second method consisted of measuring out two samples of 20 ml of vinegar in different containers and adding phenolthalein indicator to only one of them. Then adding 1 M NaOH until it turned slightly pink and then mixing the two samples of vinegar together; both buffers pH was measured and recorded. When making the second buffer it is important to remember that the quantity was determined by when the color turned slightly pink during the titration as opposed to the first buffer which was made by calculating and measuring the reactants. The approach for the second buffer is subjective to the person doing the experiment and may vary from person to person. To correct this problem the buffer was adjusted by adding a strong acid or base depending on what was needed until the pH reached 5. After the buffers were made and pH’s recorded, their buffer capacities were found and recorded as well. Even though both had a pH of 5, their buffer capacities differed greatly due to the amount of acid and bases that were found in each one. The first buffer was made with 50 ml of vinegar as opposed to the 40
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This note was uploaded on 03/08/2010 for the course CHEMISTRY 1310 taught by Professor Williams during the Spring '10 term at Georgia Institute of Technology.

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Exp10 - Discussion: This experiment dealt with acid/base...

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