Calorimetry Lab

An article titled, “The Calculation of Formation Curves of Metal Momplexes from pH Titration Curves in Mixed Solvents” showed a graph of typical titration curves, and the graphs curves and tendencies matched the graph developed in this experiment. Supporting the pH change inclinations described in the previous paragraph. “Buffers for pH and Metal Ion Control” by D. Perrin, also found that pH buffers resist changes in pH; “which were practically unaffected by the presence of traces of (acidic or basic) impurities… far from… dilute strong acids and

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.

Weight 10 dry post-82 pennies which get 77.12g, using 30ml initial volume measuring the volume of 10 pennies, record the data 9.1ml. Using equation Density= Mass/Volume, get the density of the pre-82 pennies is 8.47g/ml. Then calculate the error%=0.04%, and the deviation%=7.13%.

What would you have to do in order to increase the accuracy of this experiment, i.e, decrease the standard deviation? What I think my group could have done was instead of measuring the weight of the copper’s one time and then recording the number, we could of measured it at least twice in order to make sure our number was accurate. Our standard deviation was 2.9, although it is not a very big number, we could of minimized it if we had the correct measurements. 4. Suppose you performed this experiment, and the percent difference from the accepted value of the density of copper and your value was very large, let's say 300%.

We will observe the reaction of a buffer solution with added acids or bases. We will then evaluate buffering capacity in response to additions added from dilute acid and bases to the buffer.

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.

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

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

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.

Some of the constants kept in this experiment were the amount of vinegar, the amount/size of the materials, the surrounding temperature, the same type of equipment used and the same person determining the pH

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

This experiment was designed to test the pH changes of a weak acid, acetic acid, when it is titrated with a strong base, NaOH. We conducted this experiment so that we could obtain a pH titration curve and from this, we can correlate and signify the relationships between pH, pKA, and the ratios between the acetic acid and NaOH. This practical was key to developing our understanding of buffers and how they accept and donate protons, how this inhibits pH changes, and how this mechanism can be used for in vitro laboratory experiments. Acetic acid, CH3COOH, is described as a ‘weak’ acid as when it dissociates in water, only a very small proportion, one proton, is transferred to a water molecule. (Experimental Biology Lab Manual 2017) This experiment would also allow us to determine the pKA, the measurement of an acid’s ability to give up its protons to water. The addition of NaOH to acetic acid, results in more of the acetic acid to be dissociated into CH3COO- and H+ ions. These protons then can react with the OH- ions to form water. This reaction is in equilibrium and is fairly rapid. The Henderson-Hasselbach equation can be used to determine the pH:

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.