This lab has the following two concepts: synthesis of acetylsalicylic acid and analysis of acetylsalicylic acid. Synthesis is a purposeful execution of chemical reactions to obtain a product. This concept is used in the first part of the lab; when we have to produce crystals of aspirin. Analysis is the separation, identification, and quantification of the chemical components of natural and artificial materials. This concept is used throughout the lab when we are analyzing different reactions that are happing during the duration of the lab. The goal of this lab is to synthesize a sample of acetylsalicylic acid, otherwise known as aspirin.
This is the most important goal of the lab. This, however, has side goals that go along with the main one. One is finding the percent yield of the synthesis. Another is measuring the melting point of the aspirin sample, which will in turn indicate the purity of the sample. The last is conducting a colorimetric analysis on the aspirin sample. The educational goals of this lab are to find the structural formulas for salicylic acid, acetic anhydride, and aspirin and to use these structural formulas to construct a reaction equation by describing the synthesis of aspirin.
In addition, you have to be able to use your percent purity calculations to determine the percent yield of your synthesis of aspirin. Methods and Materials Part I: Synthesis Aspirin Goggles were obtained and put on before entering the lab area. 2. 0 grams of salicylic acid should be measured and placed into a 125 mL Erlenmeyer flask. 5. 0 mL of acetic anhydride and 5 drops of 85% phosphoric acid was added to the Erlenmeyer flask. Drops of distilled water were added to rinse down bits of solids that were on inner wall of the flask. Mixture was heated on the hot plate for fifth-teen minutes, at 75 degrees Celsius.
Two mL of distilled water was added 10 minutes into heating. Buchner funnel and filter were set up for the filtration process. Reaction was completed and 20 mL of distilled water was added to the flask. Flask was cooled for 5 minutes in an ice bath. Aspirin crystals were formed after cooling of the flask. Contents were transferred into Buchner funnel assembly. The mixture was filtered with the assistance of the vacuum. When all liquid had drained out, suction was stopped. Then 5 mL of cold distilled water was added and after 15 seconds the vacuum was turned back on.
This procedure was repeated two more times in the same manner. Aspirin crystals were stored in a safe place for purity test. Part II: Test the Melting Temperature of an Aspirin Sample Temperature Probe was connected to the Lab Quest deceive and new file was opened. About 0. 2 grams of aspirin was placed into the mortar. The pestle was used to pulverize the aspirin inside the mortar. A capillary tube was obtained. Aspirin was packed to the 1 cm marked inside the capillary tube. Capillary tube was fastened to the temperature probe by a rubber band.
A mineral bath was heated up on the hot plate. Capillary tube-Temperature Probe was immersed inside mineral oil bath. The melting point was recorded as precise as possible. A second test was conducted with a new sample of aspirin in a new capillary tube. Part III: Test the Colorimetric Absorbance of an Aspirin Sample Next, about 0. 20 g of salicylic acid was recorded. It was then transferred to a 250mL beaker and 10mL of 95% ethanol was added and swirled until it was all dissolved. 150mL of distilled water was then added and mixed with the solution in the beaker.
The contents were then placed into a 250mL volumetric flask. Distilled water was added until it hit the 250mL mark on the flask. The molar concentration was calculated and recorded. Next, four standard solutions of varying concentrations were created. 100mL of the standard solution was prepared with 10mL of the previously made solution into a volumetric flask. 0. 025 M Fe(NO3)3 solution was added to make precisely 100mL. The first trial used 10. 0mL salicylic acid and 0mL water, the second used 7. 5mL salicylic acid and 2. 5mL water, the third used 5. 0mL salicylic acid and 5.0mL water, and the fourth used 2. 5mL salicylic acid and 7. 5 mL water.
Now the calorimeter was used to collect data. The cuvette was removed and the water inside of it was removed and it was rinsed out twice. Next the device was calibrated. Afterwards, use each of the four solutions, separately, and place it in the cuvette to determine the molar concentration. This is repeated until all needed concentrations are found. Next the graph of absorbance vs. concentration was viewed on the LabQuest. Each point on the graph shows the concentration as well as absorbance.
The results were recorded. “Curve Fit” was selected from the Analyze menu. Linear as the Fit Equation was selected and the equation was recorded. Next, the aspirin sample was prepared for testing. 0. 40g of the sample was massed and transferred to the 250mL beaker. 10mL of 95% ethanol and 150mL distilled water was added and mixed into the solution. This solution was put from the 250mL volumetric flask to a 100mL volumetric flask. 0. 025 M Fe(NO3)3 was added until there was precisely 100mL in the flask. Next the absorbance of the aspirin was recorded using the calorimeter.
The cuvette was filled 3/4 with the sample. It was then placed into the device and measured. This was repeated two times. All of the materials were then cleaned up, put away, and discarded as directed Results Part I: Synthesis of Aspirin Sample Trial 1 Mass of Salicylic acid used (g) Volume of acetic anhydride used (mL) Mass of acetic anhydride used (vol 1. 08 g/ml) Mass of aspirin synthesized (g) Trial 1 Mass of Salicylic acid used (g) Volume of acetic anhydride used (mL) Mass of acetic anhydride used (vol 1. 08 g/ml) Mass of aspirin synthesized (g) Part II: Melting Temperature Data Trial 1.
Melting Temperature (Celsius ) Trial 1 Melting Temperature (Celsius ) Part III Salicylic Acid Standard Stock Solution Sample Initial mass of salicylic acid Moles of salicylic acid (mol) Intial molarity of salicylic acid (M) Initial mass of salicylic acid Moles of salicylic acid (mol) Intial molarity of salicylic acid (M) Part III Beer’s Law Data for Salicylic Acid for Sample Standard Solutions Trial Concentration (M)Absorbance 1 2 3 4 Trial Concentration (M)Absorbance 1 2 3 4 Best-fit line equation or the salicylic acid standards Best-fit line equation or the salicylic acid standards.
Test of the Purity of the Synthesize Sample Aspirin Initial mass of aspirin sample (g) Absorbance of aspirin sample Moles of salicylic acid in aspirin sample (mol) Mass of salicylic acid in aspirin sample (g) Mass of aspirin in sample (g) Percent aspirin in sample (%) Initial mass of aspirin sample (g) Absorbance of aspirin sample Moles of salicylic acid in aspirin sample (mol) Mass of salicylic acid in aspirin sample (g) Mass of aspirin in sample (g) Percent aspirin in sample (%) Questions and Calculations 1. What is the theoretical yield of aspirin in your synthesis?
The mole ratio is 1:1 between salicylic acid and acetic anhydride in this reaction. 2. The melting temperature of pure acetylsalicylic acid is 135 degrees Celsius. Based on the results of the melting temperature test, what is the percent purity of your sample of aspirin? 3. Based on the results of the absorbance testing with the colorimeter, what is the percent purity of your sample of aspirin? Does this percent purity compare well with the results of the melting temperature test? Explain. 4. Use your percent purity calculations to determine the percent yield of your synthesis of aspirin. 5.
Use your test, or another suitable resource, to find the structural formula for salicylic acid, acetic anhydride, and aspirin. Use these structural formulas to construct to construct a reaction equation describing the synthesis of aspirin. Questions and Calculations of Sample Numbers 1. What is the theoretical yield of aspirin in your synthesis? The mole ratio is 1:1 between salicylic acid and acetic anhydride in this reaction. 2. The melting temperature of pure acetylsalicylic acid is 135 degrees Celsius. Based on the results of the melting temperature test, what is the percent purity of your sample of aspirin?
3. Based on the results of the absorbance testing with the colorimeter, what is the percent purity of your sample of aspirin? Does this percent purity compare well with the results of the melting temperature test? Explain. 4. Use your percent purity calculations to determine the percent yield of your synthesis of aspirin. 5. Use your test, or another suitable resource, to find the structural formula for salicylic acid, acetic anhydride, and aspirin. Use these structural formulas to construct to construct a reaction equation describing the synthesis of aspirin. Discussions.
My beginning question before I started this lab was “What will happen if you do not measure and record the absorbance of the treated aspirin sample within five minutes? ” I did not get an answer to my question because I recorded and measured my aspirin way under the five minute period. If I did go over, however, I would think that my substance would become useless and I would have to start all over again. Also in the direction it says that this aspirin must be done quickly. Another question that came to my prior to starting the lab was “Does adding distilled water affect the overall purity of the substance?
” In my case, yes adding distilled water does affect the overall purity of the aspirin. Why? That’s because throughout the lab I had to constantly add more distilled water. In part II when we had to but the crystals into the funnel, in my case the crystals were frozen to the bottom. So I had to keep adding water for it to come out and I had to add even more water to get out the crystals that were stuck on the side of the funnel. Although I followed the directions to the best of my ability, they were quite confusing which caused numerous amounts of errors. It was all going well until part II, which involved the capillary tube.
This part was absolutely ridiculous because it was extremely difficult to get the beat up aspirin inside the tube. Once we finally got it filled and put it in the mineral oil bath, the rubber band melted before the aspirin; which made no sense. After many try however, we finally got it all to work in our favor and got a pretty good melting point. Another error that occurred in my lab due to the direction was in the preparation of the stock salicylic. The way it was written kept confusing me, so much that I took me five times to finally make the solution properly. It was not only a waste of material but also time.
There were also case that were out of my reach. The first being the evacuating of the room because someone solution started to smoke up. Also, the unexpected fire drill that throw almost everybody off. In my opinion to avoid all of this, the lab should be split into two days. The first day being Part 1 and 2 because that took a little less than 2 hours. The next day only consisting of part 3 because it was extremely complicating. My overall performance in this lab was a little above average. It seemed that I had a good start because I got an amazing yield on my overall aspirin crystal.
In my opinion if I could have somehow avoided all the errors that caused me to waste my time, the lab would have been a success. Conclusion In the end, this lab helped me understand some key concepts that I didn’t have a good understanding of before. This also helped me important laboratory procedures and techniques. I also learned a very important lesson; which was that you need to read the lab more than just once or else you will not be able to conduct it smoothly. Other than that, this lab was a very interesting type of learning experience and I hope we do many labs like this in the future.