Chemical Forums
Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: Wanderer0 on March 20, 2019, 12:12:33 PM
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I am to make a suspension of equal parts of Fe(II)SO4 and CuSO4 in equal proportion to a total of 4% (w/v)
I am making the suspension from ferrous sulfate heptahydrate and copper sulfate pentohydrate. The solvent will be water, but the final solution has to be basic pH~9.0.
How can I achieve stability of the ferrous sulphate in such pH?
I would ideally be able to retain stability for several hours.
Thanks in advance
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Have you tried yet? Are you seeing the ferrous sulfate crash out?
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I think that will not work, at alcaline pH both will precipitate as hydroxide.
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Yes, I did see precipitation. However I am not sure if Fe2+ has oxidased to Fe3+ and then reacted (it most probably has).
Is there any way of making a suspension of the two salts to render it stable for several hours?
If both salt hydrates were dissolved in water in equal amounts, would Fe2+ oxidise to Fe3+ or would it bind copper out of its sulfate?
Thank you very much for your help.
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To clarify:
I need to spread FeSO4 and CuSO4 on an area that will be moist and contain organic compounds to observe the effect for several hours - up to 8.
I will obtain salts from their heptahydrate and pentahydrate forms.
Is there another solvent that would allow me to spread these salts on the test area and that would allow the active components (iron- ferrous and copper) to be released during the period?
I am basically observing the effects of these specific metals on an area, and they must be spread out in their sulphate form.
The test area will be moist, and there will be organic compounds on it, but this is not my interest.
Is there a better solvent or medium for distributing these salts on an even surface? Would a glycerol/aqueous/alcohol composition reduce Fe2+ oxidation?
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At pH ~ 9 you will have insoluble iron (II) and copper hydroxides. If they have contact with air (which also contains carbon dioxide), hydrated iron (III) oxide will form very quickly. The basic copper carbonate will be formed slower.
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thank you for all the answers.
After dissolving the Cu pentahydrate, I am left with Cu2+ and SO42-
From the ferrous sulphate i have also SO42- and a Fe2+.
Will Fe2+ ions continue binding to SO42- until all are oxidased?
I have never had such a case, and this problem is above my knowledge of the subject.
Any contribution is most welcome
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Will Fe2+ ions continue binding to SO42- until all are oxidased?
Ions in the solution, after dissociation, are not bound to any specific ion. The only thing that matters is that the solution is electrically neutral, what ions are present doesn't matter.
Ions can react and interact, making complexes or precipitates, but that's not the case of Fe2+ and SO42- (or, rather - complexing properties of SO42- are way too low to matter).
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Neither in crystals nor in solutions of ionic compounds have covalent bonds between ions. The total formula informs us only about the composition of the stoichiometric unit of the compound.
After graduation, the chemist has intellectual tools to imagine the structure of a not very complicated chemical compound from its total formula (not always correctly, but he knows where to check it), e.g. copper sulfate pentahydrate in the crystal has a structure [Cu(H2O)4]SO4·H2O, and in the solution there are ions [Cu(H2O)6]2+ next to hydrated sulfate ions with undefined stoichiometry of water molecules (and therefore the water is omitted in ions, or it is included in the form of SO42-(aq) and then when balancing chemical reactions we neglect this (aq).
At pH 9, the solution also contains 10,000 times more OH- ions than the H3O+ ions. For both salts, the concentration of hydroxide ions is sufficient to immediately produce Cu(OH)2 (anhydrous) and Fe(OH)2 (hydrated with undefined stoichiometry)
You can find the rest in good textbooks.
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Borek, AWK; also chenbeier and Mitch:
Thank you very much for help with your responses.
I am not a chemist, (unfortunately), but I am required to reproduce an experiment that requires a chemical formulation.
My interest is in the effect of iron and copper salts on an exposed organic surface, and these observations are in my field of expertise.
However, the presented chemical formulation was unclear to me since it stated that an aqueous solution or a gel (which would be much easier to apply) are required, and that pH which allowed iron and copper to remain stable in the desired form would be from 8,5-10,5. Also, the formulation stated ferrous ion as an active component and given the basic environment, I could not make sense of it since ferric iron would appear very soon, and the observations were to be performed for 12 hours.
I am now wondering about potential pH modifiers.
Once again, thanks.
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Our pleasure Wanderer0. Keep us updated on your project!