Reaction of coloured metal complexes with water and sulfuric acid

I recently started researching the coloured compounds made from transition metals focusing on one with oxidation state II, so Mn,Fe,Co,Ni,Cu and Zn with all of them in hydrated metal sulfate complexes.

I've done some research and found why they have their colours. However I still do not know what metal ligand complex will my compounds will make when reacted with water and concentrated sulfuric acid?

Knowing the end product would help me in formulating the reaction equation and would be easy to understand for the presentation.


closed as too broad by Mithoron, user55119, Mathew Mahindaratne, Todd Minehardt, Nilay Ghosh Jun 16 at 4:44

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ If your question is about the composition, synthesis and appearance for all compounds with $\ce{M(H2O)_$x$SO4}$ formula (M = Mn, Fe, Co, Ni, Cu, Zn), then it seems to be very broad. $\endgroup$ – andselisk Jun 15 at 18:12
  • $\begingroup$ @andselisk I just chose this from a few experiments that were available and we aren't expected to go too deep. I need to explain why they have different colours, google helped with that and also show the reaction equations forming the coloured compound which i am not a 100% sure about. For Fe(II) it would be green and the complex would be $\ce{[Fe(H2O)6]^2+}$ but I don't know what complex the others would make. $\endgroup$ – muhammad haider Jun 15 at 18:27
  • $\begingroup$ Your question is slightly unclear to me: your question states that you want to know what the reaction of metal complexes with conc sulfuric acid is, but comment says otherwise. $\endgroup$ – William R. Ebenezer Jun 16 at 2:50

If a metal is made to react with sulfuric acid, it will form a sulfate salt. When you dissolve those sulfates in water, you would be studying the color of the aquated metal ion. Sulfate is just a counter ion in each case. Search crystal field theory.

You are right, iron (II) sulfate in water would be light green, Zn would be colorless, Mn would be light pinkish, nickel would be green, copper would be blue. This is the color of aquated metal ion i.e. when the central metal ion is surrounded by six water molecules.

  • $\begingroup$ and would the general formula for each of these complexes be $\ce{M(H2O)^2+_$6$}$ where M = Mn, Fe, Co, Ni, Cu, Zn? Crystal Field Theory would then explain why they have different colours? $\endgroup$ – muhammad haider Jun 16 at 12:11
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    $\begingroup$ Yes, you are right. $\endgroup$ – M. Farooq Jun 16 at 14:09

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