At the end of the experiment, seven groups also prepared different solutions. The first group was prepared by adding 1 mL of 100 mM HCl to the falcon tube containing 20 mL of PBS and the pH value was decreased from 7.4 which is the pH value of PBS to 6.22. The second group added 1 mL 20 mM HCl into the falcon tube which contain 20 mL PBS and the pH value was reduced from 7.4 to 7.22. The third group added 1 mL 2 mM HCl to the falcon tube containing 20 mL PBS and the pH value was increased fom 7.4 to 7.8. In the three groups, the same volume of different millimoles was added to the falcon tube containing the same volume of PBS. Due to the inhibition of pH change by PBS substance, it is expected that there is not much change in the pH value of the prepared solutions. As the first group used more millimolar substance, it decreased the pH value more than the second group.
In the first two groups the expected situations have occurred. However the expected results in the third group did not materialize.
In the third group, the pH value is expected to decrease due to the
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The fifth group brought 1 mL 20 mM HCl to the falcon tube which include 20 mL distilled water and the pH value was decreased from 6.65 to 5.48. The sixth group put 1 mL 2 mM HCl in the falcon tube which contain 20 mL distilled water and pH value was reduced from 6.65 to 6.22. The pH value is expected to decrease when acid added into the water, and this is also true in the three groups. The decrease in pH values at different ratios depends on the use of different millimolar substances. The first group received 1 mL of 100 mM HCl and the pH value was further reduced compared to the second and third group. Because the third group used substances from at least a few millimolar, the pH value changed very
We only added a small amount of HCl to the water and sodium chloride. We did not continue to add more HCl after a significant drop in pH was recorded. We added a total of 2 mL of HCl to both H20 and NaCl before the pH changed. The 1 gram solution of sodium acetate and acetic acid changed after a 8 mL, and the other two never dropped before we reached our total of 10 mL HCl.
3. Test was half filled with deionized water. 4. This test tube was heated and shaked until the salt was dissolved and a clear solution was prepared. Testing pH of prepared solution: 1.
The purpose of the experiment was to determine how a buffer works and how to use an acid-base indicator. The way a buffer works was determined by observing the changes in pH of solutions of different concentrations weak acids and their conjugate bases to determine how a buffer affects the pH change. The solution of 10 mL of 0.20 M CH3COOH and 10 mL of 0.20 M CH3COONa had slighter changes in pH than the solution of 10 mL of 0.0020 M CH3COOH and 10 mL of 0.0020 M CH3COONa. Both of these solutions were buffers, shown because they had slighter changes in pH than the solutions with only the weak acid or conjugate base and water. The determination of how buffers work was also tested with observing that the solution of NaC4H3O4 and Na2C4H2O4 had smaller
To improve the results from the experiment buffer solutions that were not whole pHs could have been used e.g. pH 4.5, 5.5 etc. This would have provided more reliable results as a wider range of results would have been produced. Using pHs with decimals would also help to more accurately determine the optimum pH as the optimum may have been above or below the pH stated in the hypothesis; 8. In this experiment however the optimum is taken at 8 because the graph does not rise again.
Buffer capacity is the change the pH value by a unit of 1.0. 0.1M of HCl and 0.05M of NaOH were titrated into 1x PBS buffer, and from the molarity concentration calculation done to find the pH change of 1 unit, we can conclude that the buffering capacity increased as the concentration of the buffer of acid/base solution increases. We can confirm that the closer the buffered pH is to the pKa the greater the buffer capacity, and the further it is from the pKa the more difficult it is for the buffer to resist changes in ph. Collected from the internet, the pKa of PBS is 2.16, 7.21 and 12.31. by looking at table 2, our starting pH of HCl titration was 7.37 and while the starting pH of NaOH is 7.34 we can say that NaOH has a greater
weak bases). After ranking the pH of these solutions, you will then test your predictions in the laboratory.
First, three titration curves and three second derivative curves were created to determine the average pH at the half-equivalence point from the acetic acid titrations. Titration curves were used as visuals to portray buffer capacity. The graphs and a table, Table 1, that showcased the values collected were created and included below. The flat region, the middle part, of Figures 1, 2 and 3, showed the zone at which the addition of a base or acid did not cause changes in pH. Once surpassed, the pH increased rapidly when a small amount of base, NaOH, was added to the buffer solution. Using the figures below and
For this experiment the materials included: three beakers, three antacid tablets, water at three different pH values, pH test strips, a graduated cylinder, a thermometer, a timer, a piece of paper to record results, and a pencil. To begin the experiment, each table gathered their supplies, and measured out twenty five milliliters of the solution that had a neutral pH into the first beaker, labeled beaker A, and tested the solution for its pH using a pH test strip. Next, the students dropped one of the antacid tablets into beaker A and, with the timer, timed the rate of reaction and, after the reaction was done, measured the temperature of the water in degrees Celsius with the thermometer. The students then measured twenty five milliliters of the solution that was acidic into the second beaker, labeled beaker B, and again tested for the pH of the solution with a pH test strip. The class then did the same process as aforementioned the class dropped one antacid tablet into the beaker, and measuring its rate of reaction and temperature in degrees Celsius using a thermometer.
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
2. Following solutions are added to the tubes and the pH of each tube is determined:
In this experiment, the group was given two unknown solutions and were told to discover the pH of each solution and if the two unknown solutions could be neutralized. The question they were solving for was; “How do you determine whether two solutions are acids or bases and whether these two solutions will neutralize each other and change their pH level?” The hypothesis the group decided on was; “We predict that if the unknown solutions are acids they will turn the blue litmus paper red and if they are basic, they will turn the red litmus paper blue. We predict that one of the two unknown liquids will be acid and the other will be base, so if the two unknown solutions were put together, they will neutralize each other and have a pH around 7.” There was no other research done on this project.
An experimental error would be the way neutralization was detected. Using phenolphthalein to indicate when the pH of the product solution was basic was an inappropriate method for the obtainment of accurate data because slight changes in the shades of pink which can be imperceptible to eye can indicate a different pH value and phenolphthalein only changes colour when a solution has a pH of 8.2. This could have affected the results in that one might continue to add drops of sodium hydroxide to the solution even if it was already slightly pink thus indicating it was basic. Also, to determine how many drops were required to neutralize the solution 1 drop was subtracted from the number of drops required to basify it. This could have affected the
For this experiment, a pH meter was used so this part of the experiment began with the calibration of the pH meter with specified buffers. The buret was then filled with the standard HCl solution and a set-up for titration was prepared. 200g of the carbonate-bicarbonate solid sample was weighed and dissolved in 100 mL of distilled water. The sample solution was then transferred into a 250-ml volumetric flask and was diluted to the 250-mL mark. The flask was inverted several times for uniform mixing. A 50-mL aliquot of the sample solution was measured and placed unto a beaker. 3 drops of the phenolphthalein indicator was added to the solution in the beaker. The electrode of the pH meter was then immersed in the beaker and the solution containing the carbonate-bicarbonate mixture was titrated with the standard HCl solution to the phenolphthalein endpoint. Readings of the pH were taken at an interval of 0.5 mL addition of the titrant. After the first endpoint is obtained, 3 drops of the methyl orange was added to the same solution and was titrated with the standard acid until the formation of an orange-colored solution. Readings of the pH were also taken at 0.5 mL addition of the titrant.
The pH probe of the device was rinsed in distilled water between every measurement to return back the pH of the probe to a neutral pH, and between tests to avert cross contamination of solutions. This procedure was repeated two times for attaining Waterfall Gully, Johnston’s Creek and Port Adelaide River pH. The Dhaka water sample was tested via titration method which is used to measure the unknown concentration of a known reactant. This involves reacted a known volume of a known concentration solution (a standard solution), with a measured volume of the volume of unknown concentration. The solutions are mixed until they just react completely. In an acid-base titration, an indicator allows to determine when the reaction has reached an endpoint. The method for titration used was that a burette was rinsed with 10ml of 0.1M NaOH(aq). A stand, clamp and flask were obtained and set up making sure there was about 5cm between the burette and the flask. Stopcock of burette must be shut, then the burette was filled with 0.1M NaOH(aq) until the reading was between 0 and 1ml. This value was then recorded as initial value. The 20ml pipette was cleaned with 5ml of HCl. 20ml HCl was transferred to 250ml conical flask. 5 drops of phenolphthalein were added. The titration began by opening stopcock to add 0.1M NaOH(aq) to the flask. To detain a light pink colour the solution must be constantly mixing and swirling. When it starts to go
Table 2: Consists of color extract taken from a red cabbage for a natural indicator. The pH reading that was measured by using the pH meter and the result of the pH reading to determine whether the solution was acidic or basic.