The purpose of this lab is to understand the concepts of pH and buffers and how to make a buffer in the laboratory. Also, how to perform the titration process and identify the values of pKa, equivalence point, and the unknown buffer based on the titration process.
Data Analysis
C. The buffer we prepared in the lab had an actual pH of 7.30, while the theoretical pH of the buffer was 7.25. So, we had a percent error of 0.68%. The most possible reason for the error in the percent error could be because of the experimental procedure. Probably, the beaker was contaminated with some other chemicals and prior to the experiment the beakers were not cleaned properly. The other possibility can be that the right number of chemicals were not mixed while
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Water relatively has no buffering capacity, so when we added a drop of HCl in the water the pH of water dropped from 7.97 to 6.66. This indicates that water has a weak buffering capacity. While when we added a drop of HCl in our buffer solution, the pH went from 7.30 to 7.28. It did resisted pH change well. There was a very small change in the pH. Theoretically, the pH should have dropped a few units but again this could be the experimental errors occurring during the …show more content…
Titration of Buffer of Unknown #2
pH= pKa= 7.1
Equivalence point= 11.9
H. Our unknown #1 came out to be Imidazole. We figured out the unknown by plotting the titration graph for the pH of the buffer and the volumes of HCl added to it. By the titration curve we determined the pKa and its equivalence point. We calculated the pKa of the unknown by analyzing the graph and finding out the inflection point. The inflection point was 7.1 for 7.2 mL of HCl. The pKa was 7.1 which is closest to the value of imidazole. Our value is a bit higher which could be because of the experimental errors.
In addition to that, the equivalence point was found at pH of 11.9 at 3.86 mL of HCl titrated. The formula of imidazole is C3H4N2, so the molecular weight calculated to be 67.22 g/mol. The experimental errors could be the equipment’s being contaminated or during the titration process. We had error while dispensing the volume of HCl. Me and my partner dispensed 0.3 mL instead of 0.2 at one point. This might have affected the results. There could also be possibly an error in the weighing machine while measuring 800 g of the unknown
In this experiment, there were several objectives. First, this lab was designed to determine the difference, if any, between the densities of Coke and Diet Coke. It was designed to evaluate the accuracy and precision of several lab equipment measurements. This lab was also designed to be an introduction to the LabQuest Data and the Logger Pro data analysis database. Random, systematic, and gross errors are errors made during experiments that can have significant effects to the results. Random errors do not really have a specific cause, but still causes a few of the measurements to either be a little high or a little low. Systematic errors occur when there are limitations or mistakes on lab equipment or lab procedures. These kinds of errors cause measurements to be either be always high or always low. The last kind of error is gross errors. Gross errors occur when machines or equipment fail completely. However, gross errors usually occur due to a personal mistake. For this experiment, the number of significant figures is very important and depends on the equipment being used. When using the volumetric pipette and burette, the measurements are rounded to the hundredth place while in a graduated cylinder, it is rounded to the tenth place.
When given a test tube of the unknown sample, four drops of 6 M HCl(aq) was first added in order to precipitate the ions into their respective chlorides, AgCl(s), Hg2Cl2(s), PbCl2(s), if present. After adding the HCl(aq) to the sample, the solution would turned milky white and a white precipitate settled to the bottom of the test tube, indicating that there was at least one of the ions initially present in the unknown solution. A large amount of HCl was not added because the AgCl(s) and PbCl2(s) would otherwise form soluble chloro complexes with the excess chloride atoms: PbCl42-(aq) and AgCl2-(aq). The solution was then centrifuged to fully separate the suspended chlorides from the liquid. An additional drop of HCl was then added to the
15ml of Buffer Solution at pH 8.4 produced the amount of oxygen required in 0.44cm³ per second. On the other hand, 15ml of Buffer Solution at pH 4.4 produced this amount of oxygen in 1.45cm³ per second. We can clearly see that when the Buffer Solution's pH concentration is increased, this has the same effect on the speed of the reaction, which is the effect of pH on the
I decided to experiment with pHs within the range pH 2 to pH7, as I
Discussion: The percent of errors is 59.62%. Several errors could have happened during the experiment. Weak techniques may occur.
Secondly all dilutions were made by hand, not included into the raw data was a multitude of errors which occurred when the dilution was prepared wrong. Potentially the dilutions were prepared correctly, and rather the solutions were not uniform in nature. For example the way the dilution occurred was if the required molarity was 0.05 of A and the supplied was 0.2 molar of A. 10 ml of A could be taken and 10 ml of water could be added, to make a 20 ml 0.1 molar solution of A. Next take 10 ml of the new solution and add 10 ml of water, and the 0.05 molar solution of A is formed. The flaw is thought to be in the third part of the procedure, as 0.1 molar of A is thought to have been taken out of the second solution but rather the 0.2 molar has not been correctly mixed through, and as such the final molarity is not what was calculated. This effects all the data found as the majority of points found used dilution which potentially were not correctly performed.
One possible source of experimental error could be not having a solid measurement of magnesium hydroxide nor citric acid. This is because we were told to measure out between 5.6g-5.8g for magnesium hydroxide and 14g-21g for citric acid. If accuracy measures how closely a measured value is to the accepted value and or true value, then accuracy may not have been an aspect that was achieved in this lab. Therefore, not having a solid precise measurement and accurate measurement was another source of experimental error.
Also, it had provided enough trials to find an accurate volume of Ca(OH)₂. The data collected gave enough information to find the mol of H⁺ ions which equaled the mol of OH⁻ ions because of neutralization. Furthermore, this helped to find the concentration of OH⁻, which helped find the concentration of Ca²⁺ because every 2 OH⁻ ions have one Ca²⁺ ion. That is why the concentration of Ca²⁺ was half of the concentration of OH⁻. With these two concentrations the Ksp was found which was 2.92 x 10^⁻⁵. The actual Ksp is 5.5 x 10^⁻⁶, therefore, there is a big difference. In fact, the percentage error is 431%. This could of happened because of some sources of errors in the
an unknown amino acid. A titration curve is the plot of the pH versus the volume
The first component in the Mobile phase is phosphate buffer (pH 2.5) and the second component is methanol. The elution was isocratic eluting at 30% of the buffer and 70% of the methanol at a flow rate of 1mL min−1, The wavelength used for UV-detector was 280 nm, HPLC column C18 (150 mm×4.6 mm, 5µm), and the injection volume was 20 µL.
From looking at the results I can conclude that when the pH was 3 and
Titrations are performed to calculate the unknown concentration of solutions using standard solutions. A solution of known concentration and volume is added to a solution of known volume and unknown concentration, a burette is used to find the exact amount of the known solution is required for the reaction to come to completion. A pH indicator is used to determine when a reaction has completed.
second test tube also add 6 mL of 0.1M HCl. Make a solution of 0.165
In this experiment three different equations were used and they are the Stoichiometry of Titration Reaction, Converting mL to L, and Calculating the Molarity of NaOH and HCl (Lab Guide pg. 142 and 143).
This produce a 0.1M difference from the expected value which is 1.0 M. The discrepancy between the expected and actual values could be potentially caused by a few errors or misconducts. In this case, the use of solid sodium carbonate could donate to an error because of its hygroscopic nature which means it absorbs moisture from its surrounding which could increase its weight and affect the calculations. Besides that, the volume of hydrochloric used to neutralise the sodium carbonate could also be incorrect because of the possibility of overshooting which means a drop of hydrochloric acid accidentally drips into sodium hydroxide after the endpoint has already been achieved. The result is also changed due to contamination of beaker or flask because of failure in thoroughly rinsing them. Therefore, older excess solutions could potentially mix with the hydrochloric acid or sodium carbonate and change the volume, concentration, or product