Irresistible Lab
Irresistible?
By Elizabeth Potter
December 5, 2012
Lab Section 503
Abstract The over all goal of the Irresistible lab was to verify a buffer’s ability to resist changes in pH with consecutive 1mL additions of either a strong acid (HCl) or base (NaOH). The experiment entailed preparing a combination 10 buffered and non-buffered solutions and then monitoring the pH changes as a strong acid or base was added to the solution. By performing this experiment, it was found that with increasing amounts of buffer in the prepared solutions there was better resistance against pH changes. This was because the strong acid or base was converted to it’s weak conjugate. The solution with little or no buffer had no resistance to pH changes. The Irresistible …show more content…
experiment strengthens the notions of buffer capacity because it reveals the fact that higher concentrations of a buffer provide better resistance to pH change.
Introduction The objective of the Irresistible?
Lab was to analyze the properties that buffer posses when resisting changes in pH. This was done by “testing the ability of buffered and unbuffered solutions to resist changes in pH with the addition of strong acids and bases (Lab Manual 2012-2013).” To discover the buffer ability of a solution, 10 solutions were made with varying amounts of distilled water, NaCl, C2H3NaO2, and HC2H3O2. The beakers labeled with the numbers 1-5 were determining the buffer’s ability to neutralize the strong acid HCl. The beakers labeled 6-10 were utilized in determining the buffer’s ability to neutralize the strong …show more content…
base. My lab group hypothesized that the beakers containing solutions with grater amounts of C2H3NaO2 with the constant HC2H3O2 would bring about the greatest resistance to change in pH by acting as a buffer. A buffer, which is composed of an acid or base and its weak conjugate, resists pH change by converting strong acids/bases to weak bases/acids. This leads to only partial ionization of the acid or base and the ability to resist considerable changes in pH. Therefore, greater amounts of buffer should resist changes in pH better than small amounts of buffer or lack of a buffer.
Method The experiment started with pouring each of the 10 beakers with varying amounts of distilled water, NaCl solution, C2H3NaO2 and HC2H3O2 as specified by our lab manual. Beaker 1 had 50mL of distilled water. Beaker 2 held 50mL of aqueous NaCl. The third beaker contained 1 g of C2H3NaO2 and 50mL HC2H3O2. Beaker4 included 5g of C2H3NaO2 and 50mL HC2H3O2. The fifth beaker was filled with 10g of C2H3NaO2 and 50mL of HC2H3O2. The rest of the beakers, 6-10 contained exactly what each of the first 5 beakers held (Lab Manual, 2012-2013). Next my group set up the Lab Pro system to track changes in pH. For the first 5 beakers, we used the Lab Pro system to determine the pH change with each consecutive 1mL addition of 1. 0 M HCl solution until a totally of 10mL of HCl had been added. When there was a significant change in the pH, the buffer was destroyed. In the last 5 beakers, the Lab Pro was also used only this time to determine changes in pH with continual 1mL additions of 1.0M NaOH until a total of 10mL of NaOH had been added. Again when there was a significant change in pH, the buffer was considered destroyed. All pH readings were recorded in the appropriate tables from the lab manual. The actual procedural steps are from the UNL Chemistry 110 2012-2013 Lab Manual by J. Kautx et al.
Results
Our experimental results were consistent with our prediction in that increasing the amount of C2H3NaO2 and HC2H3O2 buffer resulted in a greater ability to resist pH changes with the addition of a strong base. We stopped collecting data once the pH was constant due to our TA’s instruction. The raw data gathered our experiment is given below:
Table 1. The Effect of Acid on Solutions mL of HCl | Beaker 1 | Beaker 2 | Beaker 3 | Beaker 4 | Beaker 5 | 0 | 7.01 | 6.17 | 4.63 | 5.54 | 6.13 | 1 | 5.86 | 2.17 | 4.57 | 5.53 | 6.12 | 2 | 2.61 | 1.85 | 4.55 | 5.51 | 6.11 | 3 | 2.21 | | 4.52 | 5.49 | 6.09 | 4 | 1.99 | | 4.51 | 5.47 | 6.08 | 5 | 1.78 | | 4.49 | 4.45 | 6.06 | 6 | | | 4.47 | 5.44 | 6.04 | 7 | | | 4.45 | 5.42 | 6.02 | 8 | | | 4.43 | 5.41 | 6.01 | 9 | | | 4.41 | 5.39 | 5.99 | 10 | | | 4.38 | 5.38 | 5.97 |
Table 2. The Effect of Base on Solutions mL of NaOH | Beaker 6 | Beaker 7 | Beaker 8 | Beaker 9 | Beaker 10 | 0 | 7.29 | 10.28 | 5.5 | 6.5 | 7.34 | 1 | 11.67 | 12.64 | 11.31 | 9.72 | 9.23 | 2 | 12.17 | 12.82 | 12.21 | 12.35 | 9.98 | 3 | 12.34 | 12.9 | 12.67 | 12.87 | 11.42 | 4 | 12.55 | 12.96 | 12.68 | 12.94 | 12.65 | 5 | 12.92 | | | | | 6 | 12.96 | | | | | 7 | 13.03 | | | | | 8 | 13.11 | | | | | 9 | 13.19 | | | | | 10 | 13.23 | | | | |
Table 1 charts the data collected for the addition of the strong acid HCl, while Table 2 summarizes data gathered for the addition of the strong base NaOH. In both tables, the first two solutions showed sudden changes in pH within the first two additions of the strong acid/base. This is because the distilled water and NaCl solution are not buffers and, therefore, cannot resist the increasing acidity or alkalinity of the solution. However, once C2H3NaO2 and HC2H3O2 were added, the buffer components were able to resist pH changes. The highest level of resistance occurred with the highest mass of C2H3NaO2 as seen in Graphs 1 and 2.
Graph 1. Comparison of mL HCl Added and ∆pH for Buffered Solutions Graph 2. Comparison of mL NaOH Added and ∆pH for Buffered Solutions
The major changes in pH didn’t happen when the mass of C2H3NaO2 increased. In both the acidic and basic solutions increasing mass of C2H3NaO2 in HC2H3O2 led to increased resistance to pH change, creating a better buffer. When no buffer was present the solution showed no resistance to pH change. Discussion The major emphasis of this experiment is that buffers are more efficient when present in larger quantities.
When the amount of C2H3NaO2 increased and HC2H3O2 stayed the same, resistance to pH quantities increased. By keeping the HC2H3O2 concentration the same in each solution, we were able to identify the addition of more C2H3NaO2 as the sole factor causing increased resistance. The results found backup my group’s original hypothesis that predicted that greater amounts of C2H3NaO2 in the constant amount of HC2H3O2 would result in the greatest resistance to pH change by acting as a buffer in the solution. The buffer capacity, which is the increased about of acid or base that can be added to a buffer without destroying it’s effectiveness increased with greater amounts of C2H3NaO2. As the buffer ratio of C2H3NaO2 to HC2H3O2 increased in the solution, more acid or base was needed to destroy the buffer due to the solution’s advanced buffering capacity. When a buffer reaches capacity, the buffer has converted all the acid or base possible to it’s weakened conjugate form. Any additional amounts of acid or base after this point cause a rapid pH change in the solution. A possible experiment that builds on the concept that is explored in Irresistible? would be to compare buffer efficiency at varying temperatures. This new experiment would illustrate whether or not buffers have specific temperatures where they are most efficient or if buffers work at every temperatures. To
improve the performed Irresitable? experiment, it would be helpful to standardize all of the measurements within the experiment. Measurements made by students, are full of potential human error. Exact measurements would increase the accuracy of the results and would also allow us to better guess the buffering capacity within the solutions. Conclusion The Irresistible lab illustrated the ability of buffers to resist pH changes due to additions of either strong acid or base. Solutions that lack buffer components showed rapid changes in pH with small increments of acid or base being added. However, when a buffer was present in the solution, resistance to pH changes increased because the added acid/base was converted to its weak conjugate. The results found in this experiment also backup the concept of buffer capacity. This concept asserts that the more concentrated a buffer is the larger capacity it will have to function as a buffer. This is seen in the experiment because higher concentrations of C2H3NaO2 in HC2H3O2 resulted in greater resistance to pH changes within the solution. References Kautz, J., Carr, J., and McLaughlin, C. 2012-2013 Irresitible? Chemistry 110 Laboratory Manual, Haden McNeil. 81-92
By Elizabeth Potter
December 5, 2012
Lab Section 503
Abstract The over all goal of the Irresistible lab was to verify a buffer’s ability to resist changes in pH with consecutive 1mL additions of either a strong acid (HCl) or base (NaOH). The experiment entailed preparing a combination 10 buffered and non-buffered solutions and then monitoring the pH changes as a strong acid or base was added to the solution. By performing this experiment, it was found that with increasing amounts of buffer in the prepared solutions there was better resistance against pH changes. This was because the strong acid or base was converted to it’s weak conjugate. The solution with little or no buffer had no resistance to pH changes. The Irresistible …show more content…
experiment strengthens the notions of buffer capacity because it reveals the fact that higher concentrations of a buffer provide better resistance to pH change.
Introduction The objective of the Irresistible?
Lab was to analyze the properties that buffer posses when resisting changes in pH. This was done by “testing the ability of buffered and unbuffered solutions to resist changes in pH with the addition of strong acids and bases (Lab Manual 2012-2013).” To discover the buffer ability of a solution, 10 solutions were made with varying amounts of distilled water, NaCl, C2H3NaO2, and HC2H3O2. The beakers labeled with the numbers 1-5 were determining the buffer’s ability to neutralize the strong acid HCl. The beakers labeled 6-10 were utilized in determining the buffer’s ability to neutralize the strong …show more content…
base. My lab group hypothesized that the beakers containing solutions with grater amounts of C2H3NaO2 with the constant HC2H3O2 would bring about the greatest resistance to change in pH by acting as a buffer. A buffer, which is composed of an acid or base and its weak conjugate, resists pH change by converting strong acids/bases to weak bases/acids. This leads to only partial ionization of the acid or base and the ability to resist considerable changes in pH. Therefore, greater amounts of buffer should resist changes in pH better than small amounts of buffer or lack of a buffer.
Method The experiment started with pouring each of the 10 beakers with varying amounts of distilled water, NaCl solution, C2H3NaO2 and HC2H3O2 as specified by our lab manual. Beaker 1 had 50mL of distilled water. Beaker 2 held 50mL of aqueous NaCl. The third beaker contained 1 g of C2H3NaO2 and 50mL HC2H3O2. Beaker4 included 5g of C2H3NaO2 and 50mL HC2H3O2. The fifth beaker was filled with 10g of C2H3NaO2 and 50mL of HC2H3O2. The rest of the beakers, 6-10 contained exactly what each of the first 5 beakers held (Lab Manual, 2012-2013). Next my group set up the Lab Pro system to track changes in pH. For the first 5 beakers, we used the Lab Pro system to determine the pH change with each consecutive 1mL addition of 1. 0 M HCl solution until a totally of 10mL of HCl had been added. When there was a significant change in the pH, the buffer was destroyed. In the last 5 beakers, the Lab Pro was also used only this time to determine changes in pH with continual 1mL additions of 1.0M NaOH until a total of 10mL of NaOH had been added. Again when there was a significant change in pH, the buffer was considered destroyed. All pH readings were recorded in the appropriate tables from the lab manual. The actual procedural steps are from the UNL Chemistry 110 2012-2013 Lab Manual by J. Kautx et al.
Results
Our experimental results were consistent with our prediction in that increasing the amount of C2H3NaO2 and HC2H3O2 buffer resulted in a greater ability to resist pH changes with the addition of a strong base. We stopped collecting data once the pH was constant due to our TA’s instruction. The raw data gathered our experiment is given below:
Table 1. The Effect of Acid on Solutions mL of HCl | Beaker 1 | Beaker 2 | Beaker 3 | Beaker 4 | Beaker 5 | 0 | 7.01 | 6.17 | 4.63 | 5.54 | 6.13 | 1 | 5.86 | 2.17 | 4.57 | 5.53 | 6.12 | 2 | 2.61 | 1.85 | 4.55 | 5.51 | 6.11 | 3 | 2.21 | | 4.52 | 5.49 | 6.09 | 4 | 1.99 | | 4.51 | 5.47 | 6.08 | 5 | 1.78 | | 4.49 | 4.45 | 6.06 | 6 | | | 4.47 | 5.44 | 6.04 | 7 | | | 4.45 | 5.42 | 6.02 | 8 | | | 4.43 | 5.41 | 6.01 | 9 | | | 4.41 | 5.39 | 5.99 | 10 | | | 4.38 | 5.38 | 5.97 |
Table 2. The Effect of Base on Solutions mL of NaOH | Beaker 6 | Beaker 7 | Beaker 8 | Beaker 9 | Beaker 10 | 0 | 7.29 | 10.28 | 5.5 | 6.5 | 7.34 | 1 | 11.67 | 12.64 | 11.31 | 9.72 | 9.23 | 2 | 12.17 | 12.82 | 12.21 | 12.35 | 9.98 | 3 | 12.34 | 12.9 | 12.67 | 12.87 | 11.42 | 4 | 12.55 | 12.96 | 12.68 | 12.94 | 12.65 | 5 | 12.92 | | | | | 6 | 12.96 | | | | | 7 | 13.03 | | | | | 8 | 13.11 | | | | | 9 | 13.19 | | | | | 10 | 13.23 | | | | |
Table 1 charts the data collected for the addition of the strong acid HCl, while Table 2 summarizes data gathered for the addition of the strong base NaOH. In both tables, the first two solutions showed sudden changes in pH within the first two additions of the strong acid/base. This is because the distilled water and NaCl solution are not buffers and, therefore, cannot resist the increasing acidity or alkalinity of the solution. However, once C2H3NaO2 and HC2H3O2 were added, the buffer components were able to resist pH changes. The highest level of resistance occurred with the highest mass of C2H3NaO2 as seen in Graphs 1 and 2.
Graph 1. Comparison of mL HCl Added and ∆pH for Buffered Solutions Graph 2. Comparison of mL NaOH Added and ∆pH for Buffered Solutions
The major changes in pH didn’t happen when the mass of C2H3NaO2 increased. In both the acidic and basic solutions increasing mass of C2H3NaO2 in HC2H3O2 led to increased resistance to pH change, creating a better buffer. When no buffer was present the solution showed no resistance to pH change. Discussion The major emphasis of this experiment is that buffers are more efficient when present in larger quantities.
When the amount of C2H3NaO2 increased and HC2H3O2 stayed the same, resistance to pH quantities increased. By keeping the HC2H3O2 concentration the same in each solution, we were able to identify the addition of more C2H3NaO2 as the sole factor causing increased resistance. The results found backup my group’s original hypothesis that predicted that greater amounts of C2H3NaO2 in the constant amount of HC2H3O2 would result in the greatest resistance to pH change by acting as a buffer in the solution. The buffer capacity, which is the increased about of acid or base that can be added to a buffer without destroying it’s effectiveness increased with greater amounts of C2H3NaO2. As the buffer ratio of C2H3NaO2 to HC2H3O2 increased in the solution, more acid or base was needed to destroy the buffer due to the solution’s advanced buffering capacity. When a buffer reaches capacity, the buffer has converted all the acid or base possible to it’s weakened conjugate form. Any additional amounts of acid or base after this point cause a rapid pH change in the solution. A possible experiment that builds on the concept that is explored in Irresistible? would be to compare buffer efficiency at varying temperatures. This new experiment would illustrate whether or not buffers have specific temperatures where they are most efficient or if buffers work at every temperatures. To
improve the performed Irresitable? experiment, it would be helpful to standardize all of the measurements within the experiment. Measurements made by students, are full of potential human error. Exact measurements would increase the accuracy of the results and would also allow us to better guess the buffering capacity within the solutions. Conclusion The Irresistible lab illustrated the ability of buffers to resist pH changes due to additions of either strong acid or base. Solutions that lack buffer components showed rapid changes in pH with small increments of acid or base being added. However, when a buffer was present in the solution, resistance to pH changes increased because the added acid/base was converted to its weak conjugate. The results found in this experiment also backup the concept of buffer capacity. This concept asserts that the more concentrated a buffer is the larger capacity it will have to function as a buffer. This is seen in the experiment because higher concentrations of C2H3NaO2 in HC2H3O2 resulted in greater resistance to pH changes within the solution. References Kautz, J., Carr, J., and McLaughlin, C. 2012-2013 Irresitible? Chemistry 110 Laboratory Manual, Haden McNeil. 81-92