Theoretical Yield Calc: Asprin (C9H8O4)

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Discussion Overview

The discussion revolves around calculating the theoretical yield of aspirin (C9H8O4) from a reaction involving salicylic acid (C7H6O3) and acetic anhydride (C4H6O3). Participants explore the necessary information and steps required to determine the limiting reagent and the resulting yield, addressing issues related to density and available data.

Discussion Character

  • Homework-related
  • Exploratory
  • Technical explanation

Main Points Raised

  • The original poster (OP) expresses uncertainty about how to proceed without knowing the density of acetic anhydride, which is necessary for calculating the limiting reagent.
  • Some participants suggest that the reaction is balanced, confirming a point made by the OP.
  • One participant proposes a series of steps to calculate the theoretical yield, including determining the stoichiometric number of moles of acetic anhydride and estimating its density based on typical values for organic compounds.
  • Another participant mentions using a density found online as a last resort if no other information is available.
  • There is a suggestion to consider whether the calculated density of acetic anhydride appears realistic based on known values for organic compounds.

Areas of Agreement / Disagreement

Participants generally agree that the problem cannot be solved with the information provided, particularly due to the missing density of acetic anhydride. Multiple approaches and hypotheses are presented, but no consensus is reached on a definitive method to solve the problem.

Contextual Notes

Participants note limitations in the problem, such as the lack of density information for acetic anhydride and the need for additional assumptions to proceed with calculations.

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Homework Statement


Calculate the theoretical yield of aspirin (C9H8O4).
C7H6O3 + C4H6O3 --> C9H8O4 +C2H4O2
Mass C7H6O3 = 2g
Volume C4H6O3 = 4mL


Homework Equations





The Attempt at a Solution


I am not sure where to go with this prolem at all. I can't just assume that the density of C4H6O3 is 1g/mL because it's not water, and the problem doesn't say to assume its density to be the same as water. All I could do was find the molar mass of each substance:

C7H6O3 = 138.13g/mol
C4H6O3 = 102.1g/mol
C9H8O4 = 180.17g/mol
C2H4O2 = 60.06g/mol

I also know that I have to find the limiting reagent, to actually determine the mass of C9H8O4, but doing that requires some more information. I know that I can just Google the density of C4H603, but if its not given in the problem then its assumed that there is another way. From what I know about calcualting the limiting reagent, you need either:
(1) mass reactant / molar mass reactant --> we don't have the mass of C4H603
OR
(2) volume reactant * density reactant / molar mass reactant --> we don't have the density of C4H603 either

So with the information provided, I have no idea how to calculate the mass of C9H8O4 (aspirin)
 
Last edited:
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Do you have the correct answer? It's been a while since I've done this but I'm sure I can help you figure it out.
 
Wax said:
Do you have the correct answer? It's been a while since I've done this but I'm sure I can help you figure it out.

No, we aren't given the answers for these problems.
 
Is the reaction balanced?
 
Yes it is.
 
Is this due tomorrow?
 
It's due on Thursday, but there are no office hours until after the work is due, for some reason. If all else fails, I will just use the density that I found on Google for the acetic anhydride
 
kathyt.25 said:
It's due on Thursday, but there are no office hours until after the work is due, for some reason. If all else fails, I will just use the density that I found on Google for the acetic anhydride

Cool, we still got some time then. :biggrin:
 
This is general chemistry 1 right? I have a book, let me open it up.
 
  • #10
Okay nevermind. LOL It's been too long for me. :X
 
Last edited:
  • #11
In general problem - as stated - can't be solved for the reasons OP pointed out in the first post. However, you know number of moles of salicylic acid. Try:

1. Calculate stoichiometric number of moles of acetic anhydride.
2. Calculate mass of stoichiometric anhdyride.
3. Assuming 4 mL of anhdyride mass is that you calculated iin point 3 - what would be the density of the pure anhydride?
4. Have you ever seen an organic compound with that density? Does it look realistic?
5. If not - what will be the reasonable mass of the 4 mL? Higher than stoichiometric? Lower than stoichiometric?
6. So, what is in excess?

Could be that's off and that's not what you are expected to do, but for me that gives clear answer to the problem.

Anhydride density is very close to 1 g/mL.
 

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