[roosevelt64]

Ok so I'm a High School Student and today in the chem lab i put some distilled water and one drop of manganese sulfate together and then charged two pieces of platinum in the conducting manganese sulfate with positive and negative electrodes, but the positive and the negative electrodes yielded different colors of manganese, one side a red and then brown, and the other a kind of yellow. I was wondering if what it yielded was two different ions of manganese. But I'm not sure. He said to give him an explanation tomorrow. So I could use all the help that I could get. Thank you.

[Borek]

I think you are on the right track.

[roosevelt64]

Well, my Chem teacher said that that was correct but now he wants a detailed explanation apparently, and thats where I get stuck. I guess that I'm not doing very well at being totally precise. So any in depth ideas or answers would be most helpful. Thank you

[Grundalizer]

Sounds like you have some oxidation reduction going on.  Mn, as with some other metals, have strikingly different colors depending on their oxidation state.  I am almost positive that Mn²⁺ is a yellow color, and we know Permanganate ion MnO₄^- is a violet deep purple (Which has Mn in the +7 oxidation state)

In Manganese Sulfate Mn is in the 2+ oxidation state, which gives us the yellow color.

The only other guess I'd have for the other side is MnO₂ Manganese dioxide, which is a brownish/black solid.

I'm trying to figure out what is going on though, because manganese sulfate would simply dissociate into Mn2+ and the Sulfate ion.  If you are using platinum electrodes maybe the Mn2+ is being reduced to Mn(s) but you should see one of the platinum electrodes start getting covered with the Mn metal.  I don't think Manganese dioxide would be formed but I don't know for sure.  Did you have anything else in the solution besides water and manganese sulfate?

Did you notice on which electrode (+ or -) the yellow solution was surrounding?

[cliverlong]

Sounds like you have some oxidation reduction going on.  Mn, as with some other metals, have strikingly different colors depending on their oxidation state.  I am almost positive that Mn²⁺ is a yellow color, and we know Permanganate ion MnO₄^- is a violet deep purple (Which has Mn in the +7 oxidation state)

In Manganese Sulfate Mn is in the 2+ oxidation state, which gives us the yellow color.

The following video shows changes in colour as manganese changes its oxidation state (as described above)

http://www.youtube.com/watch?v=jRQserZYXbI

[Grundalizer]

Ok, well I learned something new then, according to the video Mn in the +4 oxidation state (manganese dioxide) is yellow, not 2+ like I originally thought.  Still I don't know what accounts for the black/brown color.  It looks like Mn is either purple,green, or yellow in its varying oxidation states, but I know MnO₂ is dark brown/black as a powder.  Tell us what your teacher says.

[roosevelt64]

The yellow color was surrounding the - electrode. And really that would explain it because before it became a dark brown initially it started out as a kindof light red which was surrounding the + electrode. I probably should have mentioned that. Thank you so much for your help.

[roosevelt64]

Also, it didn't seem to be soluble. Like the manganese was being extracted from the solution as a solid surrounding the positive electrode.

[Grundalizer]

Ok, so you should have something being reduced there, again, I'm guessing its Manganese Dioxide since it is brown/black and insoluble in water

[roosevelt64]

I agree, do you think that he would want details about how the charges effect the oxidation states of Manganese?

[roosevelt64]

I mean i know thats what were talking about, but this man likes specific. Do you think that i should go more in depth about that or do you think that leaving it as an inference would be acceptable?

[Grundalizer]

So did you just take a bunch of manganese (II) sulfate and dump it in water and stick in two electrodes and hook them up to a power source?

I'm still trying to figure this all out, MnSO₄ by itself is a paleish pink crystal substance according to wikipedia(http://en.wikipedia.org/wiki/Manganese%28II%29_sulfate)

So I'm guessing it wont turn any color if you add it to water...did it?  

Once you apply the current to the cell, I would have thought Mn²⁺ would be reduced to Mn(s) which I assume would be a silvery metal looking material.  I thought free Mn²⁺ was yellow, but according to the movie up above manganese dioxide is yellow (Mn in the +4 oxidation state).  According to that wikipedia page, Manganese dioxide and sulphur dioxide give manganese sulfate, so perhaps applying a voltage reverses that, giving manganese dioxide and sulphur dioxide.  Sulphur dioxide isn't a very nice gas though, and is pretty toxic, so I can't imagine you were making that.  Did you see any bubbles from either of the electrodes?

This is also somthing to consider (its brown) http://en.wikipedia.org/wiki/Manganese_carbonate but I never heard anything about you adding a metal carbonate to solution.

Was any color observed when you first mixed the manganese sulfate in water before you put in the electrodes?



http://en.wikipedia.org/wiki/Manganese_carbonate

[roosevelt64]

No, I took water and added a drop of Manganese Sulfate. Then I took Platinum and hooked two peices up to a 6 volt battery, one was connected to the negative and one was hooked to the positive electrode. Then I placed the Platinum into the Manganese Sulfate and the water. There was no evident color before I added the charged Platinum in the Manganese Sulfate and water. When I added added them in, yes, they both started to bubble.  Then, surrounding the positive electrode came about this bright red which then later turned into seemingly insoluble brownish Manganese, and surrounding the negative electrode a slight sickly yellow Manganese formed, with no drastic changes to the yellow color. I don't know if I was creating Sulphur Dioxide, or if it has any type of odor, but no, I didn't smell anything or have any indication that it was being created.

[Grundalizer]

Ok, so I think we can say now that Mn2+ was being reduced to manganese at the cathode (+), and Mn2+ was being oxidized to MnO₂ (yellow) at the anode (-)

[roosevelt64]

Thank you very much. I let you know what what he says.