Chemistry: Aspirin, Lab Report Example

Introduction

The purpose of the laboratory was to investigate the percentage of Aspirin in different brands of pain medications.  During the 1860’s, scientists found that the active ingredient used to help reduce fevers was salicylic acid and therefore began to highly use the chemical in different types of pain killers and fever reducers.; however, salicylic acid results in numerous side effects, such as damage to mouth, esophagus and mucous membranes.  In 1899, Bayer Company discovered ethanoate ester of salicylic acid, more commonly known as “Aspirin”.  Many different companies have used this chemical in their medication products.  The goal of the study was to compare the percentage of aspirin in each product through a method of reacting aspirin (acetylsalicylic acid) with sodium hydroxide using the following equation:

C₆H₄(OCOCH₃)COOH + NaOH ? C₆H₄(OCOCH₃)COO^–Na⁺ + H₂O

Materials

The materials used in this experiment were:

2. Three samples containing aspirin ingredient.
3. 50 cm³ conical flask.
4. Alcohol (95% )10.00 cm³.
5. NaOH (sodium hydroxide) in a 0.100 mole dm^-3
6. Hydronium ion (pH) tester.

The aspirin tablets were weighed using a balance, placed into the 50cm3 conical flask, and dissolved in 10.0cm3 95% alcohol.  The solution was titrated with 0.100 mole dm^-3 solution using phenolphthalein solution as the indicator.

Data Analysis

Molar Ratio

Equation:

C₆H₄(OCOCH₃)COOH + NaOH ? C₆H₄(OCOCH₃)COO^–Na⁺ + H₂O

Referring to the equation above, the Molar Ratio between Aspirin and NaOH is 1:1.  The percentage of Aspirin in each of the tablets was calculated using the number of moles of NaOH per mole of acetylsalicylic acid (C₉H₈O₄).  As seen in Table 6, in order to calculate the % Aspirin contained in each of the tablets, the number of grams of acetylsalicylic acid was calculated using the volume of NaOH.  As seen in trial 1 for Bayer Aspirin, the volume of NaOH was 27.8 ml NaOH.  27.8 ml NaOH/ 0.10 NaOH mole= 0.00278 mole NaOH+ 0.1 ml NaOH.  (Table 6)  The number of grams of acetylsalicylic acid was calculated using the calculated number of moles for NaOH (0.00245 moles) per mole of acetylsalicylic acid (C₉H₈O₄), which has a Molecular weight at 180.2 grams per mole. In order to obtain the amount of aspirin in the solution, the number of moles is multiplied by the molar mass.  For example, in Trial 1, 0.00278 moles x 180.2 grams / mole yields the amount of acetylsalicylic acid at 0.501 g.  The calculations were repeated for each trial for each tablet.  In addition, the average amount of acetylsalicylic acid was computed for each tablet and illustrated in Figure 2.  The largest amount of acetylsalicylic acid was observed in the Countre-Douleurs Plus at 0.53g.  (Figure 1)

As seen in Table 6, the percentage of aspirin in each of the tablets was computed.  In addition, mean values for each tablet was calculated.  The degree of error was also calculated for each trial for each of the tablets. (Figure 2)  The degree of error was calculated by multiplying 0.1ml x 100%/volume NaOH.  For example, in Bayer trial 1, 0.1ml x 100%/27.8ml=0.40.  (Table 7).  The averages for each tablet were computed and illustrated in Figure 3.  The average percent errors were less than 1.0 for each substance.  The highest percent error was observed in Bayer tablets at 0.373%.  (Figure 3)

Discussion

The results of the experiment found that Bayer had the highest percentage of Aspirin compared to the other tablets.  As seen in Figure 1, Bayer contained 84.2% Aspirin; whereas, Alka-Seltzer and Countre-Douleurs Plus contained 43.7 and 62.6.  In addition, Bayer was the smallest tablet compared to Alka-Seltzer and Countre-Douleurs Plus.  (Table 6)  Furthermore, the price of Bayer was at 6.55, which is only 0.5 cent more than the Countre-Douleurs Plus.  Countre-Douleurs Plus also had a similar amount of acetylsalicylic acid in the contents compared to Bayer.  In regard to the Alka-Seltzer, there were some differences in the data collection in regard to the Alka-Seltzer tablet.  50 ml of sodium hydroxide was not sufficient and more sodium hydroxide was added resulting in gas formation and foaming.  It is possible that this may have caused some error in the data results and therefore, 43.7% may not be accurate for this tablet.  The differences in the percentages of aspirin in each tablet were predicted since this product is found in numerous pain relievers which contain various different substances, such as caffeine and buffers.  (Katz, 1996)

The experiment resulted in data clearly indicating the percentages of aspirin found in three different tablets.  The problem with the design of the experiment was the samples chosen to compare.  Three different products were used; however, the products used were for different types of symptoms.  For instance, Bayer Aspirin is an Analgesic and used for symptoms such as head ache or fever.  Alka-Seltzer, on the hand is used primarily for gastrointestinal problems.  Therefore, it would be assumed that the Bayer Aspirin contains more aspirin than a gastrointestinal product.  (Bayer, 2014)  The experiment should have used three different types of similar Aspirin products in order to compare the amount of aspirin between products for future use as a pain reliever.  In addition, there was a larger different in mass between the Bayer and Alka-Seltzer, which required more sodium hydroxide in the reaction.  As far as the procedure was conducted, the methods were taken in a step-by-step methodology.  The tablets were weighed and measured on a balance carefully and the titrations were measured with accuracy.  The accuracy of the methods can be supported with the values computed for each trial for each tablet.  In addition, the percent errors were low, suggesting the procedure was performed accurately.  Three trials for each of the tablets were sufficient to calculate a mean for each of tablet in the time allotted during the laboratory session.

Investigating and comparing the differences in percentages of the different tablets of the same type of pain reliever could provide more insight into the types of aspirin one should purchase to relieve symptoms.  In this case, there were not three of the same types of products; therefore, it is hard to compare the percentage of aspirin in a headache reliever versus a gastrointestinal product.  In addition, using the same types of products can bring awareness to the public on which products would most likely work the best.  Furthermore, cost analysis between the products can also be analyzed.

In regard to the current experiment, since additional sodium hydroxide was added to the product, the experiment should have been repeated to add additional sodium hydroxide to the other sample tablets.

Table 1.  Bayer Aspirin – 6.55 Swiss Francs. 

Table 2.  Alka – Seltzer Bayer 13.15 Swiss Francs. 

 Table 3.  Contre – Douleurs Plus Wild 6.50 Swiss Francs. 

 Table 4.  Emipirical Data for Aspirin Tablets

Table 4.  The number of moles of NaOH in each of the tablets used during the experiment . 

Table 6.  The percent Aspirin for all trials and each tablet calculated from the Mass of the Tablet and Molar Mass of Aspirin and the volume of NaOH used in the reaction.  The mean % Aspirin provided in the table for each type of tablet.

Table 7.  Degree of error and percentage values.

References

Bayer.  (2014).  Products A-Z.  Retrieved from: http://www.bayer.com/en/Products from-A-to-Z.aspx

Katz, D.  (1996).  Preparation of Aspirin and Acetaminophen.  Retrieved from:http://www.chymist.com/aspirin.pdf