Results Section

Scenario

You are a student attending the Chem Lab Days. You will find below the data obtained in the lab so you can complete the calculations just as if you were visiting the University of Waterloo!

Results

Use the given/obtained information to calculate the mass of the crude product and synthesized pure Tylenol®.

1. Crude Product:

  1. Amount of 4-aminophenol used: 3.08 g
  2. Mass of empty 100 mL beaker: 51.28 g
  3. Mass of 100 mL beaker + crude product: 54.74 g
  • Calculate the mass of crude product:   g
  • Calculate the amount of DI water needed for recrystallization:  mL

2. Pure Tylenol ®:

  1. Mass of pure Tylenol ® + 100mL beaker (same beaker used for the crude product): 53.35 g
  • Calculate the mass of pure Tylenol ®:    g

 

Calculations

Useful Data

  • 4-aminophenol: \(\ce{MW\:=\:}109.13\:\ce{g/mol}\)
  • Acetic anhydride: \(\ce{MW\:=\:}102.09\:\ce{g/mol}\), \(\ce{density\:=\:}1.08\:\ce{g/mL}\)
  • Acetaminophen: \(\ce{MW\:=\:}151.16\:\ce{g/mol}\)

Determining the % Yield

To determine the % yield we must first determine the theoretical yield (maximum mass) that could have been obtained, below are the steps needed to do this:

  1. Determine the limiting reagent: 
    (Hint: Calculate the number of moles of each reagent used) 
    1. Calculate the moles of 4-aminophenol used:    mol
    2. Calculate the moles of acetic anhydride used:    mol
    3. Therefore the limiting reagent is:
       
  1. Determine the theoretical yield in grams: 
    (Hint: Your limiting reagent determines how many moles of product you will produce).

Theoretical yield (use two decimal places):    g

  1. Determine % yield: 
    (Hint: \(\ce{\%\:Yield\:=\:\dfrac{Experimental\;Mass\;(mass\;pure\;Tylenol\;obtained)}{Theoretical\;Yield}\times100\%}\))

% yield (no decimal places):    %

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Melting Point Observation

Literature values list the melting point of acetaminophen as 168 ºC–172 ºC. The video below shows the melting point measurement of your lab sample:

Expand/Collapse Transcript

Video has no sound.

Write down the temperature displayed on the right when you see some droplets of liquid formed in the sample.

Then write down the temperature when the sample is fully liquid. This gives the melting range.

What is the melting range of the Tylenol sample?

Enter the temperature when the solid starts to melt:   °C

Enter the temperature when the solid is fully melted:   °C

 

When the experimental range (the values you entered above) overlaps with the literature values, we say that the solid is pure. How would you characterize the sample?

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