Aspirin Lab
What would happen if a wet graduated cylinder was used to measure the acetic anhydride?
Acetic anhydride when wet will react with the water molecules and form vinegar, and in our experiement we need the acetic anhydride to react with the salicyclic acid.
A student found that is product tested positive with iron (III) chloride solution. What does this test indicate?
If tested positive, it means the excess salicyclic acid was not rinsed off thoroughly. The phenol structure of the salicyclic acid would react with the Fe3 Cl soln.
A student thought he carefully followed the directions in the experimental procedure, and he expected 2.63 g of product. However, his isolated product weighted 3.05g. What would account for the excess weight?
If there was still water after the filtering process the weight could be inaccurate.
Five consideration for using the ventilation hood properly
Is the fan going to provide proper ventalation? Are the chemicals 6" back? Are the valves all turned off when not in use? Is the hood open too high? Don't put head into it Is the light on?
The active ingredient, salicyclic acid, is found naturally in the leaves of willow trees. Would it be better to use the natural form of this pain killer? Why or why not?
No, it is dangerous if too concentrated.
What is the purpose of rinsing the solid with water?
Rinses off excess salicylic acid, catalyst, product (acetic acid) and reacts with acetic anhydride creating acetic acid.
What is the purpose of rinsing with ethanol?
The ethanol is used to help with drying the crystals and getting the water off the crystals to have a proper measurement in the weight of the crystals.
Bottles containing old aspirin tablets often smell of vinegar. The presence of what chemical uses this smell? How does this chemical form?
The presence of acetic acid gives the smell of vinegar as it is the secondary product of the reaction.
The experiment required 3 drops of concentrated sulfuric acid. Why was the acid added? Would the reaction take place if this reagent were omitted?
Used as a catalyst. The reaction would still take place without it, but it would be slower, requiring more energy time.
Percentage Yield Equation
actual product/expected product* 100%
You may have observed that not all of the commercial aspirin dissolved in the added water. What would account for the undissolved material?
fillers in aspirin, like starch and glyceral, are insoluble in water
