# Chemistry question - urgent!

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#1
Hi everyone!

I *urgently* need help on this question, any assistance would be much appreciated!

Aspirin, C9H8O4, is made by reacting ethanoic anhydride,
C4H603 (M, = 102.1), with 2-hydroxybenzoic acid (Mr =
138.1 ), according to the equation:
2C7H6O3 + C4H6O3 -> 2C9H8O4 + H2O

(a) If 15.0 g 2-hydroxybenzoic acid is reacted with 15.0 g
ethanoic anhydride, determine the limiting reagent in
this reaction.

(b) Calculate the maximum mass of aspirin that could be
obtained in this reaction.

(c) lf the mass obtained in this experiment was 13.7 g,
calculate the percentage yield of aspirin.

Thanks!
1
6 years ago
#2
This is a simple stoichiometry.

Do you know what the balanced chemical reaction means? And how to read it?

Convert masses to moles first. What is the ratio of number of moles of acid to number of moles of anhydride? Is it higher than the ratio of stoichiometric coefficients? If it is, acid is in excess, if it is not - anhdyride is in excess. Use the one that is a limiting reagent to calculate theoretical yield.
1
1 year ago
#3
I know this is an old thread...I'm sorry for awakening it ...
I'm getting actual yield lesser than theoretical yield...and there is a question of this sort:

Why might the apparent yield be higher?

How should I answer? Does apparent yield mean theoretical yield?
0
1 year ago
#4
(Original post by Spannerin'moi)
I know this is an old thread...I'm sorry for awakening it ...
I'm getting actual yield lesser than theoretical yield...and there is a question of this sort:

Why might the apparent yield be higher?

How should I answer? Does apparent yield mean theoretical yield?

apparent yield means the yield you obtained. it might be higher because maybe the product is wet and water on it increases the mass
1
1 year ago
#5
(Original post by BobbJo)

apparent yield means the yield you obtained. it might be higher because maybe the product is wet and water on it increases the mass
I see... in that case , is there any way for the actual yield to be higher than the theoretical yield?
Thanks a lot for taking your time
(p.s. I know...but my doubt is about to be cleared off ^^)
0
1 year ago
#6
(Original post by Spannerin'moi)
I see... in that case , is there any way for the actual yield to be higher than the theoretical yield?
Thanks a lot for taking your time
(p.s. I know...but my doubt is about to be cleared off ^^)
no the actual yield must be less than or equal to theoretical.

the reason why they say "apparent" is because the true yield is less than the "apparent yield".

e.g you are doing a precipitation reaction to prepare a sample of insoluble salt. the residue you obtained is not fully dried. the water on it increases the mass so the yield you obtain ("apparent yield") is greater than theoretical. if you dry the residue, the "true yield" is less or equal the "theoretical yield".
0
1 year ago
#7
(Original post by BobbJo)
no the actual yield must be less than or equal to theoretical.

the reason why they say "apparent" is because the true yield is less than the "apparent yield".

e.g you are doing a precipitation reaction to prepare a sample of insoluble salt. the residue you obtained is not fully dried. the water on it increases the mass so the yield you obtain ("apparent yield" is greater than theoretical. if you dry the residue, the "true yield" is less or equal the "theoretical yield".
Ahh..I see
Then I suppose there was some error while measuring the actual mass

Thanks a lot I understood better
0
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