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Topic: Fe2+ and Fe3+ determination  (Read 8321 times)

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Offline warnie

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Fe2+ and Fe3+ determination
« on: March 12, 2008, 08:15:49 AM »
In the experiment to determine Fe2+ and Fe3+ concentration in a solution using K2Cr2O7 Fe3+ is reduced
to Fe2+ using Zn dust and H2SO4. Why can't Zn dust be used alone? (N-Phenylanthranilicacid was used as indicator) 

Offline AWK

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Re: Fe2+ and Fe3+ determination
« Reply #1 on: March 12, 2008, 11:34:28 AM »
Zn + H2SO4 = ZnSO4 + H2
Hydrogen is a reductor.
AWK

Offline warnie

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Re: Fe2+ and Fe3+ determination
« Reply #2 on: March 13, 2008, 08:18:21 AM »
Thanks
But Zn can alone reduce Fe3+.

Offline AWK

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Re: Fe2+ and Fe3+ determination
« Reply #3 on: March 13, 2008, 08:37:43 AM »
Without acid, Zn could eventually replace Fe2+ and Fe3+, but then metallic Fe will react with water to form Fe(OH)2. Using acid from Fe(OH)2 you can obtain FeSO4, hence it does not matter what mechanism of reduction is.
AWK

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