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Topic: Practical exam: Percentage yield  (Read 4615 times)

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Offline Lilly

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Practical exam: Percentage yield
« on: October 14, 2008, 10:58:23 AM »
We reacted 1g of C6H5NH3+Cl- in 30cm3 of water with 6grams of sodium ethanoate in 25cm3 of water and 2cm3 of (CH3CO)2O. To get antifebrin CH3CONHC6H5. The equation is
C6H5NH3+Cl- + (CH3CO)2O -------> CH3CONHC6H5 + CH3COOOH + HCL

I ended up with 0.21grams of antifebrin, what was the percentage yield?

This was my working out:
Mr of reactant C6H5NH3+Cl- = 129.5
Moles= Mass /Mr
1.0g/129.5=0.0077mol of reactant

Mr of anitifibrin=135
Moles=Mass/Mr
0.21 gained from experiment / 135=0.00156

0.00156/ 0.0077 x100= 20% Is this Correct according to experiment results? Thanx in advance!
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Offline Astrokel

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Re: Practical exam: Percentage yield
« Reply #1 on: October 14, 2008, 11:32:32 AM »
hey lily, it looks ok but how much exactly did you use for acetic anhydride?
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Offline Lilly

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Re: Practical exam: Percentage yield
« Reply #2 on: October 14, 2008, 03:03:46 PM »
2cm3 of ethanoic anhydride.

Thanx
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Offline Astrokel

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Re: Practical exam: Percentage yield
« Reply #3 on: October 14, 2008, 04:19:19 PM »
and the concentration or density?
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Offline Lilly

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Re: Practical exam: Percentage yield
« Reply #4 on: October 20, 2008, 07:05:49 PM »
That was not given.
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Offline Borek

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Re: Practical exam: Percentage yield
« Reply #5 on: October 21, 2008, 03:29:27 AM »
My bet is that there was an excess of anhdyride. You may safely assume that its density was not lower that 0.5 g/mL, not many liquids get that low. That means at least 1 g of anhdyride used. Compare numbers of moles of reactants calculated assuming 1g+1g.

Besides, wiki lists its density as 1.08 g/mL.
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