Lab: Hydrolysis of Acetylsalicylic Acid (Aspirin) to Salicylic Acid
Name_________________________Lab Group Name____________________
Grams:
Molar Mass:
Moles:
C9H8O4
_______
_______
_______
Acetylsalicylic Acid
H2O
_______
_______
_______
C7H6O3
_______
_______
_______
Water
Salicylic Acid
C2H4O2
_______
_______
_______
Acetic Acid
Part I: Reaction Setup
You will receive a portion of crystalline acetylsalicylic acid (C9H8O4).
Measure the mass in grams and write it in the top-left space in the table above.
Add to an Erlenmeyer flask with 50 mL of 20% HCl solution ("muriatic acid").
Place a stopper in the mouth of the flask and seal with paraffin film to prevent
evaporation of water or acid vapors. Label the flask with the name of your lab
group. Your instructor will assist you in placing it in a 60⁰ C water bath. This
reaction needs to be heated for about 40 minutes, so you will have to complete
this lab on another day. Organic chemical reactions are often slow, as carbon
forms very strong covalent bonds which have to be broken and made - it is very
common to do "setup" and "workup" on different days.
1)
Complete the reaction table above. First, calculate molar masses for both
reactants and both products, and use them to fill the second row of the table.
Now calculate your moles of starting material (C9H8O4) by dividing the mass by the
molar mass, and enter it into the table. As the coefficients in this reaction are all
1, every product or reactant must have the same number of moles: fill in the
third row of the table. Finally, calculate the grams of H2O, C7H6O3, and C2H4O2 by
multiplying moles by molar mass for each.
2)
Which class of reaction is this? Single Displacement, Double Displacement,
Synthesis, Decomposition, or Combustion? Explain why.
Part II: Reaction Workup
Add 50 mL of cold water to your reaction to fully precipitate your salicylic
acid product. Use a spatula to scrape out as much product as possible and collect
on filter paper. To obtain maximum yield, use the filtrate to rinse out all the
reaction product. Once all the product has been collected on the filter paper, you
should rinse it 3-4 times with 5 mL portions of cold water to remove leftover
acetic acid. You can detect acetic acid residue by odor, as it's basically vinegar.
Product may then be squeezed and left to dry on a pad of paper towels.
You can test your salicylic acid product by reacting a tiny amount of it with
ferric chloride solution and gently heating.
3)
What happens when you react your product with FeCl3 solution?
4)
What happens when you react your starting material with the same FeCl3
solution?
5)
Why does this indicate a chemical change has likely occurred?
Once the product is substantially dry, you may transfer it to a tared
weighing boat and obtain a mass. Please ensure product is dry before you do this.
Mass of Salicylic Acid Product: _____________________________________
Part III: Conclusions
6)
How many grams of salicylic acid product (C7H6O3) did you predict in the
table on the first page? ________________________________
7)
What was your percent yield (100 x expected / actual)? _____________