6.03 Calorimetry Lab
In this experiment, for exercise 1, the final result of pH for distilled water has increased drastically after added 2mL NaOH from 5.87 to 12.12 compared to pH 5.9, 6.9 and 7.9. Before adding 2mL NaOH, pH reading of distilled water was 5.87 which is far from neutral. This maybe because of distilled water is contaminated or the pH meter is not cleaned properly. For ∆ pH, it shows that pH 6.9 has low value which 0.16. For exercise 2, titrate starts at 11mL with pH reading of 1.52. Then continuing adding 0.5mL aliquots of NaOH into the unknown amino acid solution (A) till volume reaches 21.5mL with pH reading of pH 2.08. At 22mL, decided to add 1mL aliquots of NaOH into the unknown amino acid solution (A) till volume reaches 45mL. It pH reading
starts to increased slowly from pH 2.11 to pH 4.50 but when it reaches 42mL, it drastically increased to pH 8.04, totally different of 3.54. After 45mL, decided to change back by adding 0.5mL of NaOH into the unknown amino acid solution (A) till it reaches 69.5mL pH reading of 11.07 and at this point, titration has stopped. From the graph that has been plotted using excel, it shows that the pKa 1 of the unknown amino acid solution (A) is 1.68 and the pKa 2 of the unknown is 8.04. The unknown amino acid solution (A) could be a Cysteine.
starts to increased slowly from pH 2.11 to pH 4.50 but when it reaches 42mL, it drastically increased to pH 8.04, totally different of 3.54. After 45mL, decided to change back by adding 0.5mL of NaOH into the unknown amino acid solution (A) till it reaches 69.5mL pH reading of 11.07 and at this point, titration has stopped. From the graph that has been plotted using excel, it shows that the pKa 1 of the unknown amino acid solution (A) is 1.68 and the pKa 2 of the unknown is 8.04. The unknown amino acid solution (A) could be a Cysteine.