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Percentage yield calculation help

Can someone help me with this question, I have no clue how they got the answer or even the mr.
(edited 1 year ago)
Original post by Aleash
Can someone help me with this question, I have no clue how they got the answer or even the mr.

At A-Level, you need to use moles instead of mass for percentage yield.
You need to work out the actual yield - THIS CAN BE USED FOR MASS AS WELL.
mass:
then you got the actual yield which is 4.82
now, you got the number of moles of phenylamine which is mass (5.05) / mr (93) the number of moles is 0.05430108. You assume it is 1:1 so work out the maximum yield of C6H5NHCOCH3 which will be 135 x 0.05430108 = 7.33064516
you got theoretical = now you got actual = 4,82 and maximum 7.33
so now you do 4.82/7.33 = 0.6575 x 100 = 65.8% which is now your percentage yield.

for moles: work out number of moles fo phenylamine which is 0.05430108 which is the same as C6H5NHCOCH3 (you assume it is 1:1) but the actual yield of C6H5NHCOCH3 is (4.82/135) 0.0357037 (Mr of the product of step 1 is 135)

now you can do 0.0357037/0.05430108 = 0.6575 x 100 = 65.8% (3sf)

2 ways withe the same answer but in a-level it is always safe to do moles.
(edited 1 year ago)
Reply 2
Original post by JA03
At A-Level, you need to use moles instead of mass for percentage yield.
You need to work out the actual yield - THIS CAN BE USED FOR MASS AS WELL.
mass:
then you got the actual yield which is 4.82
now, you got the number of moles of phenylamine which is mass (5.05) / mr (93) the number of moles is 0.05430108. You assume it is 1:1 so work out the maximum yield of C6H5NHCOCH3 which will be 135 x 0.05430108 = 7.33064516
you got theoretical = now you got actual = 4,82 and maximum 7.33
so now you do 4.82/7.33 = 0.6575 x 100 = 65.8% which is now your percentage yield.

for moles: work out number of moles fo phenylamine which is 0.05430108 which is the same as C6H5NHCOCH3 (you assume it is 1:1) but the actual yield of C6H5NHCOCH3 is (4.82/135) 0.0357037 (Mr of the product of step 1 is 135)

now you can do 0.0357037/0.05430108 = 0.6575 x 100 = 65.8% (3sf)

2 ways withe the same answer but in a-level it is always safe to do moles.

Thank you so much for the detailed response I understand it now!! I’ll definitely be using the mole technique in the future thank you so much have a good day (:!
No worries! Feel free to put on any questions related to chemistry if you get stuck. I love to see them!

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