Sandeep Voleti-Period 4/5 Honors Chemistry Titration Lab Write Up
Sandeep Voleti- Period 4/5 Honors Chemistry Titration Lab Writeup
Introduction
Titration is a method, which is meant to find the concentration of either an acid or a base by adding a measured amount of it to a known volume and concentration of an acid or base1. Titration starts with a beaker or Erlenmeyer flask containing a very precise volume of the known concentration solution and a small amount of indicator, which is put underneath a burette containing the solution with unknown concentration1. Small drops of the titrant are then added to the known solution and indicator until the indicator changes which means the endpoint has been reached. Single drops of the titrant can sometimes make a permanent or temporary change in the indicator2. …show more content…
When the endpoint of the reaction is reached, the volume of reactant consumed is measured and used to calculate the concentration of solution by using the M1V1=M2V2 formula which allows us to find the unknown concentration of the solution3. M represents the molarity and V represents the volume. 3
The main purpose of using titration is in order to get to the end point. The end point is defined as when the correct ratio of acid and base are mixed together to neutralize the solution2. If the quantity of the acid and base necessary to reach the end point is equal, then the mixture is at its equivalence point2. The difference is that while the equivalence point is where you have added the right amount of solution to neutralize the solution, the end point is where the indicator actually changes color3. One scientific principle that is very common in acid-base titration is the use of indicators such as phenolthalein. For example, phenolpthalein is clear in acidic solutions and turns pink in neutral and basic solutions. During titration, phenolpthalein can be added to an acid. As drops of a basic solution are added, the H+ ions and the OH- ions will combine to form water4. As the solution gets closer to a neutral pH, the once acidic solution will start to turn pink because the phenolpthalein will change as it becomes neutral. The use of pH indicators is a major part of titration. Choosing the right indicator according to equivalence point is also a major concept. An indicator must be chosen based on the strength of the acid, the strength of the base, and how strong the solution will be when mixed together. For example, if a strong acid is mixed with a strong base, then a neutral solution will form4. Therefore, an indicator that changes color when the solution is neutral should be chosen. Neutralization is also a major principle. Acid-base neutralization is when an acid and base are mixed in order to form water and a salt, resulting in a neutral solution. This same thing is done in titration in order to determine the unknown concentration of the solution3.
Titration is used in many different ways in chemistry, although acid-base titration is considered one of the major ones. For example, titrations are used in redox reactions to determine the concentrations of the oxidizing agent and the reducing agent. In addition, they are also used in gas phases for determining reactive substances by reaction with an excess of another gas. Zeta potential titration uses iso-electric points to characterize heterogeneous substances4.
The purpose of the experiment to determine the unknown concentration of the acetic acid found in vinegar using 0.1 M HCl and NaOH solution of unknown concentration. It was predicted that if the concentration of the NaOH could be determined, then that concentration could be used to determine the concentration of the acetic acid. The methods used were acid-base titrations in order to determine the volume used of the unknown concentration solution and simple multiplication and division in order to calculate the unknown concentration.
Materials and Methods
In order to conduct this experiment, multiple steps were followed. The burette was first rinsed with some of the NaOH and all the beakers and graduated cylinders were rinsed. Then, a 150 mL beaker and a 100 mL graduated cylinder were used to measure out 40 mL of the NaOH and to add it to the buret, labeled base. After that, 10 mL of 0.1 M HCL were placed into the 100 mL beaker located under the beaker. 20 drops of phenolphthalein indicator were added using the dropper into this beaker and the beaker was swirled in circular motion in order to allow the indicator to mix with the acid. Next, the initial volumes for the acid and base were recorded. Then, the stopcock on the burette was slowly turned vertical so that the NaOH solution would drop into the HCl, one drop at a time. After every drop, the beaker was swirled. After the color change was evident and did not go away from being swirled, the stopcock was turned back into its horizontal position. The volume of the base utilized in order to titrate the acid was recorded using the burette. Following this, the titration formula was used to calculate the unknown concentration of NaOH (in molars). This experiment was conducted 3 times to have accurate results. After these three trials, a fourth trial was conducted using 5 mL of vinegar instead of the HCl in the beaker. The same procedure used above for the HCl and NaOH titration was used for the vinegar. The concentration of the vinegar was then finally determined using the titration formula. The average of the three trials for concentration of NaOH was calculated. The percent error was then calculated using the percent error formula.
Results:
As previously mentioned, the purpose of this experiment was to determine the concentration of the acetic acid in the vinegar using the concentration of the NaOH solution using acid-base titrations.
Results for Titration of 3 Trials of HCl and 1 Trial of Acetic Acid (Vinegar) Trial # | Va | Vb | 1 | 10.00 mL | Start:0.000 mLFinish:3.700 mLVb:3.700 mL | 2 | 10.00 mL | Start:0.000 mLFinish:3.750 mLVb:3.750 mL | 3 | 10.00 mL | Start:0.000 mLFinish:3.750 mLVb:3.750 mL | Vinegar | 5.00 mL | Start:0.000 mLFinish:12.100 mLVb:12.100 mL |
Figure 1
Calculations Involved With Experiment Mb Value using 0.1 M HCL and measured Va and VbTrial 1:(0.1)(10.00)=(3.700)(x) x=0.270 | Mb Value using 0.1 M HCL and measured Va and VbTrial 2: (0.1)(10.00)=(3.750)(x) x=0.267 | Mb Value using 0.1 M HCL and measured Va and VbTrial 3: (0.1)(10.00)=(3.750)(x) x=0.267 …show more content…
| Calculate the Average Mb(0.270+0.267+0.267)/3= 0.268M | Calculate the Concentration for Vinegar:(5.000)(x)=(12.100)(0.268) x=0.649 M | Calculate Percent Error:[(0.8-0.649)/0.8]x100=18.9 % |
Figure 2
Major Trends:
Figure 1 displays the results of the 3 trials of titration of HCl and the one trial with Acetic Acid.
10 ml of acid was used for all the three trials to keep a constant. During the first trial it took 3.700 ml of NaOH to titrate the HCl, in the second trial it took 3.750 ml, and in the third trial it took 3.750 ml. These differences in amounts of NaOH required to titrate the acid led to different molarities being calculated for the NaOH. The first being 0.270M and the other to being 0.267M. In order to calculate the total volume of base used, the readings from the burette from before and after titration were subtracted from each other. The average of the three molarities was found to be 0.268M for NaOH (Figure 2).
Figure 1 also displays the results of the titration of Acetic Acid in vinegar with the NaOH. As seen in the table, it took much more NaOH to titrate the vinegar than it did with the HCL, a difference of almost 9 mL. Furthermore, the Acetic Acid was also determined to have a higher concentration compared to the HCl, with a molarity of 0.649 M. (Figure 2)
Figure 2 shows the calculations that were used in order to determine the molarities of the NaOH, the total amount of base used, and the percent error for the molarity of the acetic acid. The titration formula used was: MaVa=MbVb.) The percent error calculated was 18.9%. (Figure
2).
Discussion The results found in this experiment can be summarized in the charts above. One major finding that was found in the experiment was the average concentration of the NaOH solution, which was 0.268M. This result could be found because of the properties of titration. During titration, when a strong acid and a strong base are used, the neutralization will occur when the pH is about neutral, because it has reached its equivalence point. At the equivalence point, the number of moles of acid equals the number of moles of base2. (Summary Question 2) The MV=MV formula is derived from this because Molarity multiplied by volume will give the number of moles3, and because of this, the concentration of the NaOH was able to be calculated. Since the equivalence point for this reaction was around a neutral pH, it was indicated when the indicator turned pink. Phenolphthalein was used as the indicator in this experiment because it is clear in acids, and begins to turn pink around a neutral pH. The reason that methyl orange, another common indicator, was not used instead of phenolphthalein was that methyl orange is an indicator that changes color between a pH of 3.1 and 4.45. This means that it would have changed color before the equivalence point was even reached in this experiment. (Summary Question 4) Another major finding from this experiment was that the concentration of the acetic acid was 0.649M. The reason that this was found was because the titration of the NaOH and the acetic acid allowed it. In order for the vinegar to be titrated, the sodium hydroxide solution first had to be standardized. This is because in titrations, one acid and one base is used1. Since the concentration of the vinegar, the acid, was unknown, the concentration of the NaOH, the base, had to be known. Using titrations between 0.1M HCl and NaOH, the concentration of the NaOH was found. With this concentration, it was made possible to use the MV=MV formula in order to calculate the concentration of the acetic acid in the vinegar. (Summary Question 1)
The calculated value for the concentration of the acetic acid in the vinegar was found to be 0.649 M. The actual accepted value for the concentration of acetic acid is 0.8 M. The percent error calculated for this experiment was found to be 18.9%. This shows that the value that was calculated in this experiment was about 20% wrong compared to the actual value. The value calculated was pretty close to the actual value, and showed a difference of about 1.5M. One possible source of error for this experiment could have been the fact that qualitative data was collected. As the beaker was swirled, evidence for the change to pink color was looked for. This could have impacted the results because the perception of the color pink could differ amongst different individuals. In addition, the fact that the end point is not the same as the equivalence point could have been a source of error. Since the indicator changes color after it has reached the endpoint, it is possible that the volume recorded for the NaOH could have been higher than the actual concentration. This could have caused the calculated concentration to be smaller than it actually is. Another possible source of error could be that it is possible for the solutions to be contaminated because of prior experimentation using the same solutions. This could have impacted the data by causing the read volumes to be different from what they are supposed to be. Based on this experiment, the results do support the hypothesis previously mentioned. The hypothesis was that if the concentration of the NaOH could be determined, then that concentration could be used to determine the concentration of the acetic acid. This was proven to be true since the concentration of the acetic acid in vinegar was found, and the answer was found to be near the accepted value. The purpose of acid-base titrations is to find the concentration of an unknown acid or base, using the concentration and volume of the other and the MV=MV formula.1 Since the NaOH concentration was found using titration of HCl and then the acetic acid concentration was found using the concentration of NaOH and titration of acetic acid, the hypothesis was correct.
Summary Questions:
3. In order to determine the concentration of an acidic or basic solution, the concentration of the other solution must be known. Then, a proper indicator must be chosen that will indicate the equivalence point of the reaction. For example, a indicator which changes at a neutral pH would be appropriate for a strong acid and strong base. Then, the acid and the indicator should be placed under the burette, and the base should be placed in the burette. As the base is slowly dripped into the solution, the beaker should be swirled. Once a permanent color change is evident, volume should be recorded. Using the MV=MV formula will give the unknown concentration.
5. The concentration of the acetic acid in the vinegar was 0.649M. The molar mass of acetic acid is 60 grams. This means the weight of 0.649 moles is 38.94 grams. The weight of one liter of vinegar is found to be 1,000 grams, or one kilogram. (38.94/1000)x100 will give us the mass percent, which is 3.9%. Since it has to be at least 4% by weight acetic acid, this vinegar is very close to legal but is not. Since the calculated concentration was not exactly the accepted value, this can account for the fact that this vinegar was found to be illegal. If the accepted value was used, it would be a legal sample of vinegar.
References:
1Darthmouth College. (n.d.). Retrieved from http://www.dartmouth.edu/~chemlab/techniques/titration.html
2Helmenstine, A. M. (n.d.). Retrieved from http://chemistry.about.com/od/acidsbases/a/aa082304a.htm
3Brian, M. T. (n.d.). Retrieved from http://www.files.chem.vt.edu/chem-ed/titration/titratn.html
4Bishop, M. (n.d.). Retrieved from http://preparatorychemistry.com/Bishop_Titration.htm
5 Angel C, D. D. (n.d.). Retrieved from http://bouman.chem.georgetown.edu/S02/lect19/lect19.htm
Introduction
Titration is a method, which is meant to find the concentration of either an acid or a base by adding a measured amount of it to a known volume and concentration of an acid or base1. Titration starts with a beaker or Erlenmeyer flask containing a very precise volume of the known concentration solution and a small amount of indicator, which is put underneath a burette containing the solution with unknown concentration1. Small drops of the titrant are then added to the known solution and indicator until the indicator changes which means the endpoint has been reached. Single drops of the titrant can sometimes make a permanent or temporary change in the indicator2. …show more content…
When the endpoint of the reaction is reached, the volume of reactant consumed is measured and used to calculate the concentration of solution by using the M1V1=M2V2 formula which allows us to find the unknown concentration of the solution3. M represents the molarity and V represents the volume. 3
The main purpose of using titration is in order to get to the end point. The end point is defined as when the correct ratio of acid and base are mixed together to neutralize the solution2. If the quantity of the acid and base necessary to reach the end point is equal, then the mixture is at its equivalence point2. The difference is that while the equivalence point is where you have added the right amount of solution to neutralize the solution, the end point is where the indicator actually changes color3. One scientific principle that is very common in acid-base titration is the use of indicators such as phenolthalein. For example, phenolpthalein is clear in acidic solutions and turns pink in neutral and basic solutions. During titration, phenolpthalein can be added to an acid. As drops of a basic solution are added, the H+ ions and the OH- ions will combine to form water4. As the solution gets closer to a neutral pH, the once acidic solution will start to turn pink because the phenolpthalein will change as it becomes neutral. The use of pH indicators is a major part of titration. Choosing the right indicator according to equivalence point is also a major concept. An indicator must be chosen based on the strength of the acid, the strength of the base, and how strong the solution will be when mixed together. For example, if a strong acid is mixed with a strong base, then a neutral solution will form4. Therefore, an indicator that changes color when the solution is neutral should be chosen. Neutralization is also a major principle. Acid-base neutralization is when an acid and base are mixed in order to form water and a salt, resulting in a neutral solution. This same thing is done in titration in order to determine the unknown concentration of the solution3.
Titration is used in many different ways in chemistry, although acid-base titration is considered one of the major ones. For example, titrations are used in redox reactions to determine the concentrations of the oxidizing agent and the reducing agent. In addition, they are also used in gas phases for determining reactive substances by reaction with an excess of another gas. Zeta potential titration uses iso-electric points to characterize heterogeneous substances4.
The purpose of the experiment to determine the unknown concentration of the acetic acid found in vinegar using 0.1 M HCl and NaOH solution of unknown concentration. It was predicted that if the concentration of the NaOH could be determined, then that concentration could be used to determine the concentration of the acetic acid. The methods used were acid-base titrations in order to determine the volume used of the unknown concentration solution and simple multiplication and division in order to calculate the unknown concentration.
Materials and Methods
In order to conduct this experiment, multiple steps were followed. The burette was first rinsed with some of the NaOH and all the beakers and graduated cylinders were rinsed. Then, a 150 mL beaker and a 100 mL graduated cylinder were used to measure out 40 mL of the NaOH and to add it to the buret, labeled base. After that, 10 mL of 0.1 M HCL were placed into the 100 mL beaker located under the beaker. 20 drops of phenolphthalein indicator were added using the dropper into this beaker and the beaker was swirled in circular motion in order to allow the indicator to mix with the acid. Next, the initial volumes for the acid and base were recorded. Then, the stopcock on the burette was slowly turned vertical so that the NaOH solution would drop into the HCl, one drop at a time. After every drop, the beaker was swirled. After the color change was evident and did not go away from being swirled, the stopcock was turned back into its horizontal position. The volume of the base utilized in order to titrate the acid was recorded using the burette. Following this, the titration formula was used to calculate the unknown concentration of NaOH (in molars). This experiment was conducted 3 times to have accurate results. After these three trials, a fourth trial was conducted using 5 mL of vinegar instead of the HCl in the beaker. The same procedure used above for the HCl and NaOH titration was used for the vinegar. The concentration of the vinegar was then finally determined using the titration formula. The average of the three trials for concentration of NaOH was calculated. The percent error was then calculated using the percent error formula.
Results:
As previously mentioned, the purpose of this experiment was to determine the concentration of the acetic acid in the vinegar using the concentration of the NaOH solution using acid-base titrations.
Results for Titration of 3 Trials of HCl and 1 Trial of Acetic Acid (Vinegar) Trial # | Va | Vb | 1 | 10.00 mL | Start:0.000 mLFinish:3.700 mLVb:3.700 mL | 2 | 10.00 mL | Start:0.000 mLFinish:3.750 mLVb:3.750 mL | 3 | 10.00 mL | Start:0.000 mLFinish:3.750 mLVb:3.750 mL | Vinegar | 5.00 mL | Start:0.000 mLFinish:12.100 mLVb:12.100 mL |
Figure 1
Calculations Involved With Experiment Mb Value using 0.1 M HCL and measured Va and VbTrial 1:(0.1)(10.00)=(3.700)(x) x=0.270 | Mb Value using 0.1 M HCL and measured Va and VbTrial 2: (0.1)(10.00)=(3.750)(x) x=0.267 | Mb Value using 0.1 M HCL and measured Va and VbTrial 3: (0.1)(10.00)=(3.750)(x) x=0.267 …show more content…
| Calculate the Average Mb(0.270+0.267+0.267)/3= 0.268M | Calculate the Concentration for Vinegar:(5.000)(x)=(12.100)(0.268) x=0.649 M | Calculate Percent Error:[(0.8-0.649)/0.8]x100=18.9 % |
Figure 2
Major Trends:
Figure 1 displays the results of the 3 trials of titration of HCl and the one trial with Acetic Acid.
10 ml of acid was used for all the three trials to keep a constant. During the first trial it took 3.700 ml of NaOH to titrate the HCl, in the second trial it took 3.750 ml, and in the third trial it took 3.750 ml. These differences in amounts of NaOH required to titrate the acid led to different molarities being calculated for the NaOH. The first being 0.270M and the other to being 0.267M. In order to calculate the total volume of base used, the readings from the burette from before and after titration were subtracted from each other. The average of the three molarities was found to be 0.268M for NaOH (Figure 2).
Figure 1 also displays the results of the titration of Acetic Acid in vinegar with the NaOH. As seen in the table, it took much more NaOH to titrate the vinegar than it did with the HCL, a difference of almost 9 mL. Furthermore, the Acetic Acid was also determined to have a higher concentration compared to the HCl, with a molarity of 0.649 M. (Figure 2)
Figure 2 shows the calculations that were used in order to determine the molarities of the NaOH, the total amount of base used, and the percent error for the molarity of the acetic acid. The titration formula used was: MaVa=MbVb.) The percent error calculated was 18.9%. (Figure
2).
Discussion The results found in this experiment can be summarized in the charts above. One major finding that was found in the experiment was the average concentration of the NaOH solution, which was 0.268M. This result could be found because of the properties of titration. During titration, when a strong acid and a strong base are used, the neutralization will occur when the pH is about neutral, because it has reached its equivalence point. At the equivalence point, the number of moles of acid equals the number of moles of base2. (Summary Question 2) The MV=MV formula is derived from this because Molarity multiplied by volume will give the number of moles3, and because of this, the concentration of the NaOH was able to be calculated. Since the equivalence point for this reaction was around a neutral pH, it was indicated when the indicator turned pink. Phenolphthalein was used as the indicator in this experiment because it is clear in acids, and begins to turn pink around a neutral pH. The reason that methyl orange, another common indicator, was not used instead of phenolphthalein was that methyl orange is an indicator that changes color between a pH of 3.1 and 4.45. This means that it would have changed color before the equivalence point was even reached in this experiment. (Summary Question 4) Another major finding from this experiment was that the concentration of the acetic acid was 0.649M. The reason that this was found was because the titration of the NaOH and the acetic acid allowed it. In order for the vinegar to be titrated, the sodium hydroxide solution first had to be standardized. This is because in titrations, one acid and one base is used1. Since the concentration of the vinegar, the acid, was unknown, the concentration of the NaOH, the base, had to be known. Using titrations between 0.1M HCl and NaOH, the concentration of the NaOH was found. With this concentration, it was made possible to use the MV=MV formula in order to calculate the concentration of the acetic acid in the vinegar. (Summary Question 1)
The calculated value for the concentration of the acetic acid in the vinegar was found to be 0.649 M. The actual accepted value for the concentration of acetic acid is 0.8 M. The percent error calculated for this experiment was found to be 18.9%. This shows that the value that was calculated in this experiment was about 20% wrong compared to the actual value. The value calculated was pretty close to the actual value, and showed a difference of about 1.5M. One possible source of error for this experiment could have been the fact that qualitative data was collected. As the beaker was swirled, evidence for the change to pink color was looked for. This could have impacted the results because the perception of the color pink could differ amongst different individuals. In addition, the fact that the end point is not the same as the equivalence point could have been a source of error. Since the indicator changes color after it has reached the endpoint, it is possible that the volume recorded for the NaOH could have been higher than the actual concentration. This could have caused the calculated concentration to be smaller than it actually is. Another possible source of error could be that it is possible for the solutions to be contaminated because of prior experimentation using the same solutions. This could have impacted the data by causing the read volumes to be different from what they are supposed to be. Based on this experiment, the results do support the hypothesis previously mentioned. The hypothesis was that if the concentration of the NaOH could be determined, then that concentration could be used to determine the concentration of the acetic acid. This was proven to be true since the concentration of the acetic acid in vinegar was found, and the answer was found to be near the accepted value. The purpose of acid-base titrations is to find the concentration of an unknown acid or base, using the concentration and volume of the other and the MV=MV formula.1 Since the NaOH concentration was found using titration of HCl and then the acetic acid concentration was found using the concentration of NaOH and titration of acetic acid, the hypothesis was correct.
Summary Questions:
3. In order to determine the concentration of an acidic or basic solution, the concentration of the other solution must be known. Then, a proper indicator must be chosen that will indicate the equivalence point of the reaction. For example, a indicator which changes at a neutral pH would be appropriate for a strong acid and strong base. Then, the acid and the indicator should be placed under the burette, and the base should be placed in the burette. As the base is slowly dripped into the solution, the beaker should be swirled. Once a permanent color change is evident, volume should be recorded. Using the MV=MV formula will give the unknown concentration.
5. The concentration of the acetic acid in the vinegar was 0.649M. The molar mass of acetic acid is 60 grams. This means the weight of 0.649 moles is 38.94 grams. The weight of one liter of vinegar is found to be 1,000 grams, or one kilogram. (38.94/1000)x100 will give us the mass percent, which is 3.9%. Since it has to be at least 4% by weight acetic acid, this vinegar is very close to legal but is not. Since the calculated concentration was not exactly the accepted value, this can account for the fact that this vinegar was found to be illegal. If the accepted value was used, it would be a legal sample of vinegar.
References:
1Darthmouth College. (n.d.). Retrieved from http://www.dartmouth.edu/~chemlab/techniques/titration.html
2Helmenstine, A. M. (n.d.). Retrieved from http://chemistry.about.com/od/acidsbases/a/aa082304a.htm
3Brian, M. T. (n.d.). Retrieved from http://www.files.chem.vt.edu/chem-ed/titration/titratn.html
4Bishop, M. (n.d.). Retrieved from http://preparatorychemistry.com/Bishop_Titration.htm
5 Angel C, D. D. (n.d.). Retrieved from http://bouman.chem.georgetown.edu/S02/lect19/lect19.htm