For solution 3a it is a neutralization reaction with the following expression

For solution 3a it is a neutralization reaction with

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For solution 3a, it is a neutralization reaction with the following expression, NH 3 + HCl → NH 4 Cl (9) The formation of NH 4 Cl, a salt of the neutralization reaction, would add a
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source for common ions in the hydrolysis reaction given by equation (4). This would lead to a decrease in OH - ions due to the leftward shift of the reaction. Solution 3b is another case of the common-ion effect, this time with OH - as the common ion. Its addition would increase the pH due to the reformation of the base by the leftward shift. The change in pH solutions 3a and 3b are -0.60 and +0.57 respectively. Solutions 4a and 4b follow a similar course as that of the divisions for solution 3. Again, change in pH level is minimal compared to solutions 3a and 3b because solution 4 is a buffer solution. For solution 4a, the H + ions from adding HCl reacts with NH3 producing more NH 4 + . And for solution 4b, the OH - ions from adding NaOH reacts with NH 4 + to form NH 3 . From the results in table 2, pH meter results and calculated pH results are slightly different. This is due to experimental errors and the accuracy of the used pH meter. Even so, when adding an acid, it should lower the pH level and when adding a base, it should increase the pH level. For the results in the experiment, there were no abnormalities in the trend and the said trend was followed. SUMMARY AND CONCLUSIONS For the results, pure solutions of weak acids and bases have shown to have no resistance in change of pH level when a strong acid or base is added, with a change in pH level almost nearing 1.0. Buffer solutions, on the other hand, have proven to be effective at resisting the change of pH, even avoiding drastic changes to pH. Having a buffer solution which resists the change in pH, the pH level is changed to at most 10 -1 of the change in pH level of the pure solution. Due to experimental errors in solution preparation, there might have been slight inconsistencies with pH level change but it is not at all extreme. The experimental pH values might have been deviated due to the inconsistency in molarity produced and volume added of the solutions. Depending on molarity and volume change, this would have led to an increase or decrease in pH level. Aside from that, the pH level could be also altered when the pH meter was used. The pH meter, a sensing mechanism, may have been contaminated. By contaminated, it may not have been thoroughly washed or cleansed with distilled water thus, leading to slight inaccuracy. If contaminated with an acid, it might have led to a lower reading and if it was with a base, a higher reading. Overall, the experiment was a success. There were slight errors but since three methods in calculating for the pH level were used (calculations, visual indicators, and pH meter), the results from these methods were compared and each result verified each other. It is recommended that, if this experiment were to be repeated, careful solution preparation and thorough cleaning of containers and the pH meter should be advised.
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  • Fall '17
  • Sir Jaden Smith
  • pH, Buffer solutions, NH3

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