C-343-2:3 - Lab Experiment 2 and 3 combined report. PDF

Preview

Summary

Lab Experiment 2 and 3 combined report. ...

Description

Miller 1 Jaylee Miller Mahmoud Arab C-343-2/3 6 Oct. 2019

Data/Results: Table 1: The Composition of Panacetin Name Sucrose Aspirin

Mass (g) Given Percentage by mass Experimental Percentage by Mass Experimental Percentage by Mass After Recrystallization

Tylenol (Unknown)

0.21 10%

0.19 40%

2.39 50%

Unknown (After Recrystallization ) 0.75 50%

7.53%

6.81%

85.66%

N/A

18.26%

16.52%

N/A

65.22%

Table 1 displays experimental data, specifically mass, through the use of multiple lab procedures. The percentage by mass was given and then calculated for the actual amount of mass that was recovered through the lab.

Equation 1: Percent Recovery 2.79 grams recovered of Panecetin x 100 %=91.48 % recovery 3.05 gramsused of Panecetin Equation 1 shows the calculation that was performed to determine the percent recovery through the use of experimentally gathered mass of Panacetin and the amount of Panacetin used.

Equation 2: Percent Recovery 1.15 grams recovered of Panecetin after recrystalization x 100 %=37.7 % recovery 3.05 grams used of Panecetin Equation 2 displays the calculation that was performed to determine the percent recovery through the use of the experimentally gathered mass of Panacetin after recrystallization of the unknown.

Table 2: Melting Points of the Unknown Compound Name of Melting Point – Trial 1 Melting Point – Trial 2 Compound (ºC) (ºC) Phenacetin 135 (given value) Acetanilide 114 (given value) Unknown 111.1-112.0 111.1- 113.7

Miller 2 Jaylee Miller Mahmoud Arab C-343-2/3 6 Oct. 2019

Unknown + acetanilide Unknown + phenacetin

112.3-114.7

111.6-114.7

109.3-110.6

109.7-110.5

Table 2 portrays experimental data that was obtained through lab procedures, which can be seen as melting ranges for each substance. The melting points of Phenacetin and Acetanilide were given values.

Discussion Aspirin → Sodium Acetylsalicylate

Sodium Acetylsalicylate → Aspirin

There are many over-the-counter pain-killers available currently. The two types of painkillers consist of analgesic drugs which reduce pain and antipyretic which reduce fevers. These two types can also be seen in just one of these OTC drugs such as Tylenol. The compound this lab focuses on is Panacetin which can be considered both analgesic and antipyretic due to its composition. This specific drug is known to contain about 10% sucrose, 40% aspirin, and 50% of an unknown substance. It was thought that this unknown compound was Tylenol, but inconsistencies have shown that it may contain an illegal foreign formulation. The purpose of this lab was to separate this unknown from the other substances and then test it through melting point to figure out if it is either Acetanilide or Phenacetin. This separation was done through the use of solubilities, filtration, and recrystallization. Notable data for this experiment can be seen above in the tables and equations. The main focus with this lab is the percent by mass of Panacetin obtained with can be seen in Table 1 as 18.26% sucrose, 16.25% Aspirin, and 65.22% of the unknown. For this part of the experiment, there were many errors that could have been made due to the various steps when separating each

Miller 3 Jaylee Miller Mahmoud Arab C-343-2/3 6 Oct. 2019 component. The percent by mass that was obtained for sucrose was higher than expected, a few reasons on why this could have occurred was due to inaccurate weighing technique or liquid of the filtrate being present when weighing the sucrose. A way to improve this measurement would be to more carefully weigh the mass along with making sure that the yield is completely dried. A low percent by mass for Aspirin could be seen as well. An error that could have caused this not properly mixing the organic and aqueous layers; if this occurred it could be the reason for why the unknown is a higher percentage than expected as well. To improve both of these errors simultaneously, proper mixing in the separatory funnel is needed. To do this, it is important to wash the mixture until needed and make sure to combine the two so that all substances should be in the correct layer. When recrystallizing the unknown to get rid of impurities, it is possible that there was too much water used, which could lead to a loss of product based on solubility. To correct this error, it would be important to gradually add water to make sure that no extra water is added once completely dissolved. Another notable point is in Equation 2 which shows that the percent recovery from the initial mass of Panacetin used was less than 37.7% which shows a loss of product and is a result of the previous errors mentioned. When deciding what the unknown compound is, it was vital to experimentally find the data that is presented in Table 2. This table shows that when mixed with both compounds it is more likely to be Acetanilide. The melting point of the mixture with Phenacetin lowered due to impurities being present when added to the unknown; this decrease is caused by being loosely packaged. Lastly, when focusing on the melting point of the unknown versus the mixtures with Phenacetin and Acetanilide, it is seen that the “unknown” is still lower than the closest compound which was Acetanilide. This could be caused by impurities still being present within the unknown which would thus lower the melting point. To improve this error, the previous ideas listed could aid in a purer substance overall, especially when separating the aspirin from the unknown. All of the above discussed improvements could lead to a better percent by mass for each compound along with a closer measured melting point to the determined substance. Overall, this experiment was successful in answering the question proposed for this lab. The unknown compound was identified through the use of separating the components of Panacetin and then melting point was used to determine that the unknown was Acetanilide. It is important to mention that although it was a success, it could be better improved by improving the percent recovery which would overall lead to more accurate percent of Panacetin for each compound.

Assigned Questions Experiment 1 Question 1 - (a) Describe any evidence that a chemical reaction occurred when you added 6 M HCl to the solution of sodium acetylsalicylate. (b) Explain why the changes that you observed took place. (a) When HCl was added to sodium acetylsalicylate, a white precipitate formed from the reaction. (b) This occurred because aspirin is a weak acid compared to the acetylsalicylate ion, which means that the reaction would favor the reactants side. Question 2 - Describe and explain the possible effect on your results of the following experimental errors or variations. In each case, specify the components whose percentages would

Miller 4 Jaylee Miller Mahmoud Arab C-343-2/3 6 Oct. 2019 be too high or too low. (a) After adding dichloromethane to Panacetin, you didn’t stir or shake the mixture long enough. (b) During the NaHCO3 extraction, you failed to mix the aqueous and organic layers thoroughly. (c) You mistakenly extracted the dichloromethane solution with 5% HCl rather than 5% NaHCO3. (d) Instead of using pH paper, you neutralized the NaHCO3 solution to pH 7 using litmus paper. a) If the solution is not stirred/shaken for enough time, the components will not be dissolved completely in the DCM. This means that the sucrose yield will be impure and higher than expected while the aspiring and unknown will be lower than expected. b) If these two layers are not mixed properly, the aspirin percentage would be lower because all of it would not be turned into sodium acetylsalicylate. c) If DCM is extracted with 5% HCl, the aspirin would not turn into sodium acetylsalicylate which means that it would not have been separated from the unknown. d) If this compound is neutralized, the sodium acetylsalicylate would transform into acetylsalicylic acid which would cause the yield of aspirin to be lower. Question 5 - Write balanced reaction equations for the reactions involved (a) when aspirin dissolves in aqueous NaHCO3, and (b) when aspirin is precipitated from a sodium acetylsalicylate solution by HCl. Assuming that both reactions are spontaneous under standard conditions, label the stronger acid, stronger base, weaker acid, and weaker base in each equation. (a) HC9H7O4 (s) + NaHCO3 (aq) → NaC9H7O4 (aq) + H2CO3 (aq) Stronger Acid Stronger Base Weaker Base Weaker Acid (b) NaC9H7O4(aq) + HCl(aq) → HC9H7O4(s) + H2O(l) Stronger Base Stronger Acid Weaker Acid Weaker Base Experiment 2 Question 1 - (a) What is the minimum volume of boiling water needed to dissolve 0.200 g of phenacetin? (b) About how much phenacetin will remain dissolved when the water is cooled to room temperature? (c) Calculate the maximum mass of solid (undissolved) phenacetin that can be recovered when the cooled solution is filtered. 100 mL =16.39 mL boiling H 2 O (a) 0.200 g Phenacetin × 1.22 g 0.076 g =0.0125 g Phenacetin (b) 16.39 mL× 100 mL (c) 0.200 g−0.0125 g=0.1875 g maximum phenacetin recovered Question 2 - An unknown compound X is one of the four compounds listed in Table 2. A mixture of X with benzoic acid melts at 89 degrees Celsius, a mixture of X with phenyl succinate melts at 120 degrees Celsius, and a mixture of X with m-aminophenol melts at 102 degrees Celsius. Give the identity of X and explain your reasoning. - The identity of X is phenyl succinate. I believe this because when a compound is mixed with a different compound, the melting point of these together will be lower than either of them. This reasoning leads me to narrow down the possible identity of X because X with benzoic acid and with m-aminophenol both result in lower melting points than the pure compounds. When X was mixed with phenyl succinate, the melting point did not change which points to why I believe X is this compound.

Miller 5 Jaylee Miller Mahmoud Arab C-343-2/3 6 Oct. 2019 Question 3 - Tell how each of the following experimental errors will affect your experimental results (yield, purity, or both), and explain why. (a) You failed to dry the product completely. (b) You used enough water to recrystallize phenacetin, but your unknown was acetanilide. (c) In the “Extraction and Evaporation” Experiment, you didn’t extract all the aspirin from the dichloromethane solution. (a) If the product is not dried completely it will weigh more than it actually would if dried properly. (b) Acetanilide is more soluble in water than phenacetin, so the yield would be lower if enough water to dissolve phenacetin was used. (c) The yield of aspirin would be lower than expected. Question 4 - Tell whether each of the experimental errors in exercise 3 will affect the melting point of the unknown component. If it will, tell how it will affect the melting point, and explain why. (a) Water will be evaporated when heated since it has a low boiling point, which means that the boiling point of phenacetin would not be affected. (b) The melting point of acetanilide would not be affected although the yield is lower. (c) The aspirin is considered an impurity and would lower the melting point....