Buffers Lab

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.

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.

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.

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.

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.

A buffer solution is “a solution that undergoes a limited change in pH upon addition of a small amount of acid or base.” (Smith et al. 2014) A buffer has the ability to neutralise OH- ions and H+ ions, as it contains a weak acid-base conjugate pair, such as, NH4+/NH3, therefore, giving the solution the capability to resist changes in pH. This buffer can be prepared by adding NH4Cl (a salt) to NH3 (a weak acid). (Brown et al. 2014, p. 711)

Extended Response Task- Acid and Bases Introduction: A buffer solution is a solution (consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid), which minimises changes in pH when small quantities of acids or bases are added to it. In a way, it is used to consistently moderate the pH of a solution, and is measured using the Acid Dissociation Constant. General Formula: HA⇋H^++A^- NaA⇋N^++A^- Where HA is a weak acid, N+ is a salt, and A- is a weak base.

A buffer solution is a solution that is able to resist changed in pH with the addition of small amounts of acid or base. Acidic buffers contain a mixture of a weak acid and the acid’s conjugate base; HA⇋H+ + A- When adding acid, H+ ions react with A- making more HA, and equilibrium shifts right to reduce the amount of acid Whereas adding alkali, the OH- reacts with H+ making H2O; equilibrium shifts right to replace the lost H+. Alkaline buffers contain a weak base and its salt; NH3 + H2o⇋ NH4+ + OH- Added H+ ions (acid) react with OH- to make H2O (eqm shifts right to replace lost OH-)and added OH- (alkali) reacts with the NH4+ reforming NH3 and water (eqm shifts right to reduce the amount of NH3 + H2o).

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

2.0ml of buffer solution was taken (through the use of a graduated pipette) and 18.0ml of distilled water added to it. The pH of the solution was measured and the buffer capacity tested by the use of the procedure outlined in the previous section.

The phosphate buffer keeps the pH of the internal cell fluid at the proper pH. In the phosphate buffer H2PO4- is the weak acid

Acids and bases exist as a buffer system. For example, a mixture of a weak acid can reversibly become base or a mixture of a weak base can reversibly become acid. There are two type of acid-base imbalance; metabolic and respiratory. Metabolic imbalance is a disorder that produce an alteration in the plasma bicarbonate concentration from the addition to or the loss from the extracellular fluid of nonvolatile acid or alkali.

To make the buffer solution you need 0.2 mol dm-3 of Na2HPO4 and 0.1mol dm-3 of citric acid this will give 100cm3 of buffer. Here is how to get the different pH in the buffer solutions:

In the first experiment my partner and I selected to produce a buffer that contained 35mL of .1 M sodium acetate with 10 mL of .2M acetic acid with the excepted pH of the solution to be 5. We used C1V1=C2V2 to first calculate the theoretical concentration of both the weak acid and the weak base in the buffer solution. Then using the theoretical concentration and the Henderson- Hasselbalch equation we were able to calculate the excepted pH. After calculating the pH we then measured the experimental pH of the produced buffer and found it to be 4.9. This showcased that there was a difference of 2% between the theoretical pH and the experimental pH. We further measured the buffering capacity of three different samples one being the buffer that