Moles Watch

Stranded
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#1
Report Thread starter 13 years ago
#1
Hi,

I came across this moles question in a book;

>A student passed chlorine over heated iron until all the iron had reacted. He collected 16g of FeCl3. What % yield had he obtained?

OK, Im totally clueless coz they havent given any mass of reactants!
Can somebody pls help me with this?
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ba_ba1
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#2
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(Original post by hira89)
Hi,

I came across this moles question in a book;

>A student passed chlorine over heated iron until all the iron had reacted. He collected 16g of FeCl3. What % yield had he obtained?

OK, Im totally clueless coz they havent given any mass of reactants!
Can somebody pls help me with this?
Well it always helps to write the reaction out:

2Fe + 3Cl2 ------> 2FeCl3


Moles of FeCl3 = 16/162.5= 0.0985mol

2:3 ratio
moles of Cl2 = 0.0985 x 3/2=0.148 moles

2:2 ratio
moles Fe = 0.0985moles

I think you can work out the rest now, and i cant be arsed anyway! If you are still really stuck just PM me.
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charco
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#3
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logically, if all the iron had reacted then the yield was 100%
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Borek
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#4
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Something is wrong with the question. Just knowing mass of the product is not enough to calculate % yield.

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Borek
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supreme
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(Original post by hira89)
Hi,

I came across this moles question in a book;

>A student passed chlorine over heated iron until all the iron had reacted. He collected 16g of FeCl3. What % yield had he obtained?

OK, Im totally clueless coz they havent given any mass of reactants!
Can somebody pls help me with this?
You have been given the mass actually obtained but you need to know the mass of at least one of the reactants used. Are you sure you haven't written/copied it wrong?
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Borek
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I like charco answer

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Borek
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ba_ba1
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#7
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(Original post by supreme)
You have been given the mass actually obtained but you need to know the mass of at least one of the reactants used. Are you sure you haven't written/copied it wrong?
you can work out the mass of the 2 reactants quite easily.
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Borek
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ba_ba1: please read whole thread. Masses of both reactants are of no use with regard to the OP question. If you think opposite show how to calculate percent yield.

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Borek
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Stranded
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#9
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(Original post by charco)
logically, if all the iron had reacted then the yield was 100%
I dont know...The answer at the back of my book says 98% :confused:
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charco
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#10
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hira - do not take my answer seriously - everyone is correct (except BaBa) - there is insufficient information to calculate the percentage yield as:
percentage yield = actual yield/theoretical yield x 100

and as you cannot work out the theoretical yield without the limiting reagent mass or moles then the question is a veritable Gordian knot i.e. impossible to unravel...

Do not waste anymore finger pounding/computer keys/electrons on what is clearly a misprint...shrug shoulders and go on to greater things - and be happy, your birthday nears!
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Stranded
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#11
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OK...thank you!
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