Chemistry Question


School of Chemistry

The University of Melbourne

Laboratory Report Cover Sheet

Student Name:  
Student Number:  
Subject Name & Code:  
Experiment Title: Experiment F6: Analysis of Aspirin

Due Date: _____________________________


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  • This laboratory report is my own original work and does not involve plagiarism or unauthorised collusion, except where due credit is given to the work of others. The report is based on results and spectra obtained by me during my laboratory session.
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Experiment F6:  Analysis of Aspirin



Day/Time/Group number:



(Summary of what you did and what you found out)










Introduction and Aim:

(Why do we perform analysis?  Why is it important to know content of tablets?  How are you planning to test samples and what will you learn?  Are the tests being used here enough to tell you the exact composition and identity of the sample being tested?)















(How did you perform your experiment? Full method is not required – refer to title of source, year and publisher)





(Tables of data)

Solubility of Aspirin (This table refers to the solubility tests shown in the video for this experiment)

Test Observation
Aspirin in water  
Aspirin in NaOH (aq)  

PART A: Analysis of Commercial Aspirin

Concentration of NaOH solution: ……………………………………………


Aspirin Brand and stated content: ……………………………………………………………………………………………


Table 1. Titration of Aspirin Tablet with NaOH Solution (with extra entry boxes in case of error)


(2 decimal places)


(2 decimal places)


(mL) (2 decimal places)

Titres used for calculation


PART B: Analysis of Student Aspirin (F2)

Table 2. Titration of Student Aspirin sample with NaOH Solution

(with extra entry boxes in case of error)

Sample Mass of sample used (g) INITIAL BURETTE READING (mL)

(2 decimal places)


(2 decimal places)


(2 decimal places)




PART C: TLC Analysis of Student Aspirin

Table 3. TLC Results – show your calculation of Rf values

TLC Results/Conditions Stationary Phase



Mobile Phase




(identify by letter or number)

Rf =




(identify by letter or number)

Rf =




(identify by letter or number)

Rf =




(identify by letter or number)

Rf =



Sketch of TLC plate, with spots numbered:













(Answers to Questions and Discussions)

Question 1. (This question refers to the solubility tests shown in the video for this experiment)

What is the effect of adding NaOH, a strong base, on the solubility of aspirin?

Provide a reason for this behaviour, including the intermolecular forces that would be involved in the most soluble solution observed.










Question 2

Recall from Experiment F2, that aspirin can react with water to form salicylic acid.



As an acid, salicylic acid, can react with NaOH.


  1. Calculate the Ka of aspirin and the Ka of the two acidic sites shown on salicylic acid in the figure above, using the pKa values provided.






  1. Which is the strongest acid site of the three circled sites shown? Explain your answer (hint: what is the definition of a strong acid?).







Question 3

  1. Complete the following table:

Calculate the mass of aspirin in the commercial aspirin tablet,

Calculate the mass of aspirin in the 0.100 g of student sample from F2.

Molar mass of aspirin, C9H8O4          ………………………

CALCULATIONS FOR AVERAGE MASS OF ASPIRIN Commercial aspirin Student sample of aspirin
a)  Average titre of NaOH (mL)    
b)  Number of moles of NaOH reacted


c) Number of moles of aspirin that reacted with NaOH


d)  Mass of aspirin present (convert to mg)



Table 4. Titration results





  1. For 0.100 g sample of pure salicylic acid, calculate the volume of 0.100 M NaOH that would be required for the titration (assume 1:1 reaction between salicylic acid and NaOH).

Molar mass of salicylic acid, C7H6O3 ………………………

  pure aspirin pure salicylic acid
mass 0.100 g 0.100 g
Molar mass 180.2 g.mol-1 138.1 g.mol-1
a) Number of mole, n    
b) Number of mole NaOH required to react (assume 1:1 stoichiometry)    
c)  volume of 0.10 M NaOH required to completely react (mL)    





Question 4

  1. How accurate is your titration of the commercial tablet? Identify any errors that may have affected your analysis.







  1. How pure is your sample of recrystallized aspirin from your titration results? Identify any factors that may have affected your results

(Hint: Think about answer to 3ii above. If your synthesised aspirin sample contains any salicylic acid, would you expect your average titre to be larger than expected for pure aspirin or lower than expected for pure aspirin?)









Question 5

With reference to the TLC results and to the polarity of the mobile and stationary phases, explain:

  1. What is the identity of your recrystallized product from Experiment F2?







  1. How pure is the recrystallized product from Experiment F2?






  1. What can you conclude from consideration of the results of both the analyses: a) your titration results; and b) your TLC analysis? (Do they agree and point you to one hypothesis? Is one method more sensitive than the other?)







(What have you found out?)

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