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The Henderson-Washable equation as used to calculate an appropriate ratio of acid:base volumes in order to prepare a buffer solution with a given pH value. The main results conveyed the optimum pH range for each buffer system, where significant changes of pH value are resisted with additions of small amounts of acid or base. Introduction Our body cells have natural ability to resist excessive pH changes. Metabolic activity produces acid and to a lesser extent, base and they hydrogen ions associated can alter the overall charge, configuration and function of various proteins.

The majority of acid results from carbohydrate and fat metabolism, reducing CO, which combines with H2O to form WHICH, carbonic acid, dissociating to form H+ and HACK- ions. Most bases come from metabolism of anionic amino acids and oxidation of organic anions, producing HACK- ions. The pH changes associated are resisted by various physiological buffering systems. So preparation of a buffer system at a particular pH, as well as finding the effective pH range for different buffers, is of use as artificial buffers are therefore necessary to mimic this ability when studying biochemical processes in vitro.

The Henderson-Washable equation defines the relationship between aloes of pH and PC and the molar ratio of conjugate acid and conjugate base concentrations. PH = PC + If PC and desired pH is known, molar ratio of acid:base can be calculated. The equation was rearranged to find the ratio necessary to produce a buffer of a given PH. The aims of the experiment were: * Determination of pH ranges over which the buffering systems acetic acid/ acetate, Trip(base)/Trip (acid) and glycogen (acid)/glycogen (base) respectively are effective and plotting the associated values on a titration curve. Use and rearrangement of the Henderson-Washable equation to prepare a buffer of specific PH. Use and calibration oaf pH meter to measure PH. Method The pH meter was calibrated using solutions of pH appropriate to the titration. Volumes of glycogen and Trip (O. 1 M) were made up and acetic acid was titrated against Noah, Trip against HCI and glycogen against Noah. After each aliquot was ran in from the burette, pH values of the resulting solutions were measured and recorded. Hydrochloric acid was titrated against sodium hydroxide with pH measured in the same way, to give a comparison curve.

The ratio of acetic acid:sodium acetate was calculated through rearrangement of the Henderson- Washable equation and a buffer solution of pH 5. Was made through mixing the appropriate volumes of each. Results Aliquots of 0. MM Noah at intervals of Mil were ran into a 0. MM solution of acetic acid. The pH was measured, using a pH meter, after the addition of each aliquot. Fig 1. Shows the resulting change in pH after each Mil addition of Noah. Raw data is presented in Table 1 in the Appendix. A steady increase in pH is seen with the addition of up to ml of Noah. The pH ranges from 2. 90 – 5. 82.

The acetic acid/acetate buffer system is successfully resisting excessive changes in pH with the addition of alkali, this is the range over which the buffer system is most effective. A sharp change in pH is seen after 1 Mil of Noah is added, increasing to 1 1. 20. The PC value is 4. 56, after addition of ml of Noah. Aliquots of 0. MM HCI at intervals of Mil were ran into a 0. MM solution of Trip. The solution of Trip of 0. MM concentration was prepared using 1. Egg of Trip and mall of water . The pH was measured, using a pH meter, after the addition of each aliquot. Fig 2. Shows the resulting change in pH after each Mil addition of HCI.

Raw data is presented in Table 2 in the Appendix. A steady decline in pH is displayed with the addition of up to ml of HCI. The pH ranges from 7. 19 – 10. 51. The Trip (base)/Trip (acid) buffer system is successfully resisting excessive changes in pH with the addition of acid, this is the range over which the buffer system is most effective. A sharp change is pH is seen after ml of HCI is added, decreasing to 2. 50. The PC value is 8. 35, after addition of ml of HCI. Aliquots of 0. MM Noah at intervals of Mil were ran into a 0. MM solution of glycogen. The solution of Trip of 0. 1 M concentration was prepared using 0. G of glycogen and mall of water. The pH was measured, using a pH meter, after the addition of each aliquot. Fig 3. Shows the resulting change in pH after each Mil addition of Noah. Raw data is presented in Table 3 in the Appendix. A steady increase in pH is displayed between 1 – 1 Mil of added Noah. The pH ranges from 9. 18 – 12. 58. The glycogen (acid)/glycogen (base) buffer system is successfully resisting excessive changes in pH with the addition of alkali, this is the range over which the buffer system is most effective. The PC value is 10. 43, after addition of mm’ Noah. Aliquots of 0. M Noah at intervals of Mil were ran into a 0. MM solution of HCI, to provide a comparison titration curve. Fig 4. Shows the resulting change in pH after each Mil addition of Noah. Raw data is presented in Table 4 in the Appendix. This buffer system can resist changes in pH with the addition of a much larger volume of alkali. Up to ml of Noah was ran into the HCI, and the pH only varied from 0. 92 – 2. 20. A sharp increase is seen after the addition of ml Noah but subsequent additions up to ml did not alter the pH value significantly, suggesting that this buffer system is effective over pH ranges 0. 2 – 2. 20 and also 11. 07 – 12. 41. The PC value is 1. 11, after addition of ml Noah. In order to prepare the pH 5. 2 acetic acid/acetate buffer, a ratio of of [sodium acetate] and [acetic acid] was used. This was calculated using the Henderson- Washable equation. If PC and desired pH is known, molar ratio of acid:base can be calculated. The equation was rearranged to find the ratio necessary to produce a buffer of a given PH. Details of the calculation are given as Figure in the appendix, as Figure 5 in the Appendix. Mall 0. MM sodium acetate solution was prepared using 0. G sodium acetate and mall of water. Ml of the sodium acetate solution and ml of acetic acid were then mixed to prepare mall of O. MM acetic acid/acetate buffer solution. The pH was found to be 5. 05. Discussion The experiment aimed to determine pH ranges over which each of the tested buffer systems are effective and to use the interrelationship between pH and PC as defined by the Henderson-Washable equation to prepare a buffer at a specific PH. The acetic acid/acetate buffer was found to be effective within the pH range 2. 90 – 5. 82.

The Trip (base)/Trip (acid) buffer was found to be effective within the pH range 7. 19 – 10. 51. The glycogen (acid)/glycogen (base) buffer system was found to be effective within the pH range 9. 18 – 12. 58. The PC value is the pH where the weak acid is half neutralizes. The experiment showed that for acetic acid PC = 4. 56 in comparison to the recognized value of 4. 72, for Trip PC = 8. 5 in comparison to the recognized value of 8. 00 and for glycogen PC = 10. 43 in comparison to the recognized value of 9. 6. There is little variance present in these values, suggesting that the trends found are valid.

The PC values for each buffer system lies towards the middle of the pH range over which the system is most effective. This is because the maximum buffering capacity is found when pH = peak, and buffer range is considered to be at a pH = peak В± 1. It is clear from the respective titration curves that HCI is a more effective buffer, resisting changes in pH through addition oaf larger volume of Noah, mm’ in comparison o mi. This is due to the more complete dissociation of HCI in aqueous solution, as it is a stronger acid.

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