A student carried out the synthesis of aspirin, starting with 3.22 g of salicylic acid. After carrying out the reaction, recrystallizing and then drying the product, the student obtained 3.65 g of aspirin. Calculate the percent yield.
I'm pretty sure it's (3.65 g / 3.22 g)*100 = 113.35%.
Is that correct?
Also, could someone please explain what is meant by creating a flow diagram for this experiment?
No, you didn't do the percent yield correctly. You must use the 3.22 g salicylic acid with which you started to calculate how much aspirin you should have obtained if the reaction was 100% efficient. I hastily went through it and it is approximately 4 grams but you need to go through more accurately than I. The value you obtain is the theoretical yield. Then
%yield = (actual yield/theoretical yield)*100 = ??
actual yield is 3.65 grams.
theoretical yield (from my data) is 4 but you will have a slightly different number. A yield of greater than 100% is great if you can get it but there is no free lunch (said another way there is no perpetual motion).
To calculate percent yield, you are correct in using the formula: (actual yield / theoretical yield) * 100. However, in this case, we need to determine the theoretical yield first.
The theoretical yield refers to the maximum amount of product that could be obtained, assuming the reaction goes to completion and all starting materials are converted into products.
In the synthesis of aspirin, one molecule of salicylic acid reacts with one molecule of acetic anhydride to produce one molecule of aspirin and one molecule of acetic acid.
To calculate the theoretical yield of aspirin, you need to convert the mass of salicylic acid to moles and compare it to the balanced chemical equation. The molar mass of salicylic acid is 138.12 g/mol.
Moles of salicylic acid = mass of salicylic acid / molar mass of salicylic acid
= 3.22 g / 138.12 g/mol
From the balanced chemical equation, the mole ratio between salicylic acid and aspirin is 1:1. Therefore, the number of moles of aspirin produced is also equal to 3.22 g / 138.12 g/mol.
To convert this to grams, multiply by the molar mass of aspirin, which is 180.16 g/mol:
Theoretical yield = moles of aspirin * molar mass of aspirin
= (3.22 g / 138.12 g/mol) * 180.16 g/mol
Now that we have the theoretical yield, we can calculate the percent yield:
Percent yield = (actual yield / theoretical yield) * 100
= (3.65 g / [(3.22 g / 138.12 g/mol) * 180.16 g/mol]) * 100
After performing the calculations, you should get the percent yield of the synthesis of aspirin. In this case, it should be less than 100% because the actual yield is lower than the theoretical yield.
Regarding the flow diagram for this experiment, it is a visual representation of the steps involved in the synthesis of aspirin. It typically includes the starting materials, reagents, apparatus used, and the procedures followed in each step. The flow diagram helps to outline the sequential order of the experiment and visualize the progression of the reaction from start to finish.