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June 29, 2025, 01:46:45 pm
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jaydee

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gravimetric analysis help
« on: August 28, 2011, 06:50:31 pm »
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can someone please help me with this question - i keep getting the answer wrong  :-[

An impure sample of iron(II)sulphate, weighing 1.545g,was treated to produce a precipitate Fe2O3. If the mass of the dried precipitate was 0.315g calculate the percentage of iron in the sample
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Re: gravimetric analysis help
« Reply #1 on: August 28, 2011, 06:55:25 pm »
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n(Fe2O3)=0.315/(2*55.85+48)
=0.001972mol
so n(Fe)=2*0.001972
=0.003944mol
so m(Fe)=0.003944*55.85
=0.2203g
% by mass of Fe in sample = 0.2203/1.545 *100
=14.26 (w/w)
just double check the answer is right

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jaydee

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Re: gravimetric analysis help
« Reply #2 on: August 28, 2011, 06:59:26 pm »
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omg thankyou! i just realised i kept multiplying the number of moles of iron by molar mass of iron sulphate instead of just iron D: thanks!
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