Buffer Works Lab

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

The purpose of adding acid to water in this lab was to test the effect of adding acid to something that doesn't have buffers in it so that the pH could be compared to the animal tissue which did.

For part B, 50 mL of an assigned 50 mL pH solution of either 1 M HCl, 1 M NaOH, lemon juice, and 50 mL of household bleach all in separate 250 mL beakers are to be used. For part C, a hot plate or ice are to be used to make the 1.0 mL assigned temperature specific water. This experiment will also use the 1.0 mL of 0.1 Phosphate buffer.

The procedure of this lab is to determine if liver and potato cells contain natural buffers that resist large change in pH as 1. NaCl or 1. NaOH are added to the solution.

A buffer is a solution that resists changes in pH when H+, OH-, or H20 is added. By using standard lab equipment, a lab pro diagnostic tool, and acidic and basic solutions, the pH can be found. By recording the pH while adding a base or an acid gradually to a buffer solution you can find the capacity of each buffer to resist drastic changes in pH. The best buffers will keep a solution from becoming either too acidic or basic with the addition of a strong base or acid.

To start out this study the difference between acids and bases has to be identified. Acids have very low pHs and have a high concentration of hydronium ions, while bases have a high pH and have a high concentration of hydroxide ions. The difference between strong bases and acids, and weak bases and acids is the amount of dissociation. Strong bases and acids dissociate a large amount and let go of their ions in solution, while weak bases and acids may only let go of some of their ions. This is important because if the unknown solutions aren’t strong acids or bases then using their ions to calculate the pH of the solutions will give false results (Diffen 2012).

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.

When using different methods to measure pH levels there are some tools that can be useful. Some more than others but by putting into action the different methods it may determine which tools will work best and give the best results when testing the pH within a solution. The pH, which stands for the proportion of hydrogen ions in a solution, could be acidic (acidosis), neutral or basic (alkaline). The pH scale goes from numbers 1 through 14. A pH of 7 is neutral;

When compared to distilled water (Figure 2), the pH of the buffer solution showed a stable pH, showing only a .2 fluctuation between the solution with the strong acid (HCl) and the solution with the strong base (NaOH). Distilled water, on the other hand, showed a 10.55 fluctuation of pH from the same amounts of the same solutions added, supporting the fact that buffer solutions are able to resist pH changes. Distilled water is made of H2O ions so it isn’t able to neutralize H+ and OH- ions, it has to have another solution added to do so. The same go for other species that are simply one element or compound, they also tend to change pH more readily than buffers. Buffers have acidic compounds that are able to neutralize those ions, however they will change pH as readily as other solutions if enough of HA isn’t present.

To prevent fluctuation in the pH, a solution known as a “buffer solution” was used in the experiment. Buffer solutions are mixtures of at least two chemicals which counteract the effect of acids and alkalis. Therefore, when a small quantity of alkali or acid solution is added the pH of the enzyme doesn’t change.

Within an acid-base titration the titration curve resembles the strengths of the corresponding acids and bases. A strong acid will correspond with a weak conjugate base, and a weak conjugate acid will correspond with a strong base. This is based on the Bronsted-Lowry model. The weak acid will donate protons to the hydroxide ion. Weak acids will have a low Ka value, the Ka value is the tendency of the acid to dissociate:

By using acid-base titration, we determined the suitability of phenolphthalein and methyl red as acid base indicators. We found that the equivalence point of the titration of hydrochloric acid with sodium hydroxide was not within the ph range of phenolphthalein's color range. The titration of acetic acid with sodium hydroxide resulted in an equivalence point out of the range of methyl red. And the titration of ammonia with hydrochloric acid had an equivalence point that was also out of the range of phenolphthalein.. The methyl red indicator and the phenolphthalein indicator were unsuitable because their pH ranges for their color changes did not cover the equivalence points of the trials in which they were used. However, the

The pH of a solution is the measure of the concentration of charged Hydrogen ions in that given solution. A solution with a pH lower than seven is considered to be acidic. A solution with a higher pH is a base. It is very important for organisms to maintain a stable pH. Biological molecules such as proteins function only at a certain pH level and any changes in pH can result in them not functioning properly. To maintain these constant pH levels, buffer solutions are used. A buffer solution can resist change to small additions of acids or base’s. A good buffer will have components that act like a base, and components that act like an acid.

For this experiment, titrations on a weak acid, acetic acid, and a buffer were performed. Acetic acid was titrated with NaOH in order to observe the half-equivalence point as well as the equivalence point. Then, the buffer and the buffered acetic acid solution prepared faced additional titration with NaOH and HCl to evaluate the differing buffering effects following the addition of a strong acid and strong base. Finally, the buffer’s buffering capacity was calculated. If the experiment were to be repeated, it would be interesting to observe the buffering effects following a titration between a weak base and a buffer instead with greater concentrations. The change in the concentration following the preparation of buffer with a weak base and its conjugate acid would pose for an interesting experiment to observe an increase in the buffering capacity.

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.