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You are watching: How to calculate theoretical yield of aspirin


The post-lab questions gave are SIMILAR to questions you might encounter in your lab hand-operated. These inquiries will certainly carry out you with a step-by-step overview on just how we approached the problem. You have the right to usage this overview and the data you recorded to aid answer the concerns. Any offered examples via values will be through mock worths. Use of these worths will certainly nearly assuredly give you nonsensical calculations. They are only supposed to show the logic.


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question 1

You are asked to calculate the percent yield of aspirin, give what the worth have to be (theoretical yield), and define why your worth (actual yield) might differ from this

From the over reactivity we know the amount of salicylic acid is a 1 to 1 (1:1) proportion via the amount of aspirin. This implies eexceptionally mole of salicylic acid offered will yield the same number of moles of aspirin. Thus, the first step is to calculate the variety of moles of salicylic acid supplied. Note: you are told that acetic anyhydride is in excess and salicylic acid is the limiting reagent

Mass of Salicylic Acid Used (mock value) = 276.24 g

Molar Mass of Salicylic Acid = 138.12 g

Moles of Salicylic Acid = (1)/(2) = 276.24/138.12 = 2.000 moles


To then transform the number moles of Aspirin to the meant yield in grams, we multiply the moles by the molar mass of asprin

Moles of Salicylic Acid = Moles of Aspirin —> 2 moles of Salicylic Acid provides 2 moles of Asprin

Molar Mass of Aspirin = 180.16 g

Theoretical yield of Aspirin (g) = (2 moles)(molar mass of aspirin) = 2.000(180.16) = 360.3 grams


Percent Yield Calculation (remember considerable figures)

Your actual yield will be the amount aspirin you weighed after it was filtered and also dried in lab. Using the theoretical and actual you have the right to calculate percent yield.

Actual Yield of Aspirin in lab after filtered/dried (mock value) = 370 g

Mass of Theoretical Yield of Aspirin (mock value) = 360.3 g

Percent Yield = (Actual ÷ Theoretical) x 100 = (370 ÷ 360.3) x 100 = 103 %

Your value may differ from the theoretical value for a variety of reasons. If it is over 100%, it may be bereason your aspirin was not entirely dried. If it is below 100%, it might be because of sample loss once transporting to the weigh paper.


Concern 2

Asks you in between aspirin and salicylic acid, which reacts through FeCl3FeCl3 only reacts via copounds that have actually phenols. Determine whether aspirin or salicylic acid has a phenol and that must be the one that reacts through FeCl3


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Phenols (click to enlarge)


Question 3

Asks you to find three prevalent esters and attract the frameworks.

Just google it.


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