Titration : The Capacity Of 0.02 M Monobasic Potassium Phosphate

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Titration was used to determine the buffering capacity of 0.02 M monobasic potassium phosphate, 0.02 M dibasic potassium phosphate, a solution of equal mixture of the two, and water. Due to the mathematical relationship of pH to the concentration of hydronium ions we can interpret the results of this experiment to support the claims that monobasic potassium phosphate acts as a better buffer for bases but not acids and that dibasic potassium phosphate acts as a better buffer for acids but not bases. Similarly, a combination of the two act as the ideal buffer for the addition of both acids and bases. A weak acid and it salt can act as either an acid or a base as needed to neutralize the pH and keep it within a certain range.
To investigate these assertions, two stock solutions of 0.02 M monobasic potassium phosphate (KH2PO4) and 0.02 M dibasic potassium phosphate (K2HPO4) were prepared. These solutions were then made into 8 dilutions. Two of the dilutions were KH2PO4, two were K2HPO4, two which were a mixture of KH2PO4 and K2HPO4 and two were solely distilled water. Initial pH’s (without any added acid or base) were recorded using a pH electrode for all dilutions. Using a 50 ml buret 1 ml of acid (HCl) or 1 ml of base (NaOH) was added to each dilution and the pH again recorded. This process was repeated until a total of either 10 ml of 0.1 M HCl or 0.1 M NaOH had been added to the dilutions and the pH recorded after each 1 ml addition of HCl or NaOH.
0.02 M K2HPO4 solution

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