LSM 1101 Lab Report 1 V Essay

In this lab, the purpose was to determine the stability of a substance after adding an acid or a base. The results claim that liver and buffer are the most resistance to change in pH. Looking at figure 3, buffer and liver both maintain a stable pH even with the addition of an acid or base. However, potato and water have less buffer in them since their pHs did change. In figure 3, the potato acid’s pH level decreased by two, and the potato base’s pH level increased by two. The level of pH of a water acid decreased by 4, while the water base’s pH increased by 5. These results all tie to the fact that buffer is a substance that maintains a stable pH; the presence of buffer in organisms help maintain homeostasis by binding or releasing hydrogen

(.1063 KIO31) (1 mol KIO214 g) x 6 mol S2O41 mol KIO= .00298.04150= .259 M

The protein molecules in many foods provide the amino acid building blocks required by our own cells to produce new proteins. To determine whether a sample contains protein, a reagent called Biuret solution is used. Biuret solution contains copper ions. However, the chemical state of the copper ions in Biuret solution causes them to form a chemical complex with the peptide bonds between amino acids (when present), changing the color of the solution. Biuret solution is normally blue, but changes to pink when short peptides are present and to violet when long polypeptides are present.

1. To titrate a hydrochloric acid solution of “unknown” concentration with standardized 0.5M sodium hydroxide.

Mole of chlorine : 1.0217g - .221g - .3946 g = .4061 g of chlorine

1. Suppose that you have an unlimited supply of copper (II) sulfate to react with iron. How many moles of copper would be

pH was recorded every time 1.00 mL of NaOH was added to beaker. When the amount of NaOH added to the beaker was about 5.00 mL away from the expected end point, NaOH was added very slowly. Approximately 0.20 mL of NaOH was added until the pH made a jump. The pH was recorded until it reached ~12. This was repeated two more times. The pKa of each trial are determined using the graphs made on excel.

In your laboratory notebook sum these two reactions to find the stoichiometric factor that relates moles of

weak bases). After ranking the pH of these solutions, you will then test your predictions in the laboratory.

The purpose of this experiment was to determine the pKa, Ka, and molar mass of an unknown acid (#14). The pKa was found to be 3.88, the Ka was found to be 1.318 x 10 -4, and the molar mass was found to be 171.9 g/mol.

9. How many moles of NaOH would be needed to completely react with all of the excess HCl determined in problem 8?

ii. The second part of the titration series involves titration of NaOH with Hydrochloric acid (HCL). Again, three reps of titration and a blank titration have to be completed. A volumetric pipet is used to measure 10.00mL of HCL into three labeled conical flasks. Then the flasks are filled with deionized water until about the 50mL mark. A buret is

During a titration the pH of the solution will be monitored using a pH meter from that we get a titration curve. The titration curve is then used to determine the equivalent molecular weight and Ka value of the unknown weak acid, from that we are

3. A few drops of 6 M acetic acid were added until it became basic.

The titration curve of the unknown exhibited many characteristics, such as equivalence points, pKa of ionizable groups, isoelectric point, and buffer regions, that are particularly distinct to lysine. For unclear reasons, the pH during the titration did not reach the pH for pure 0.2 M NaOH nor 0.2 M HCl and normal equivalence points expected at two extreme ends of the titration curves for all amino acids were not observed. The titration of a phosphate buffer showed that the buffer capacity is directly proportional to the molarity of the buffer. However, our results showed that although the initial pH of the phosphate buffer was less than the pKa value, the measured buffer capacity was higher towards acid than base. The accuracy of the pH meter and calibration process was questioned under assumptions that the pH of the prepared phosphate buffer was actually above pKa.