# Redox Titration - Determining the % of Iron II and Iron III

determine the % of iron II and iron III in a mixture containing both, where i am given 200cm3 of a solution containing 1.3g of iron ions(Fe 2+ Fe 3+) using potassium magnanete.
I wrote down the equation already, and method, but i don't know how to work out the % from it :/

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symbolipoint
Homework Helper
Gold Member
Having the equation (which you tell us that you worked out) allows you to use stoichiometry and formula weights or formula masses and fairly simple basic mathematics arithmetic. Realize, your reaction is oxidation of the Fe+2 by Mn04-, to become Fe+3 (and whatever becomes of the permanganate).

How many moles, and how many grams of Fe+3 did you find? From this, find how many grams of Fe+3 is in the sample.

... is there more to your task than you wrote in your question to the forum? Do you want ALL of the iron using a permanganate titration? I would imagine that you could use an EDTA titration to find all of the iron, and then use a permanganate titration to get the Fe+2; maybe you could first reduce the Fe+3 with some well chosen reducing agent before titrating ALL of the iron with permanganate.

Yes thats right, well firstly I am trying to work out how much iron is present alltogether and how much of it is Iron II
on my task sheet all it says: You have to devise a volumetric procedure to determine the percentage of iron II and Iron III in a mixture containing both.

You are provided with 200cm3 of a solution containing between 1.1g - 1.3g of iron ions as a mixture of Fe2+ or Fe3+. You may assume that each of the 2 ions of is present to at least 30% by mass. But a balance is not avaliable.

I know that you use titration for this to find the concentration of Iron II first, but then i confused afterwards, are we suppose to make up the concentration for Potassium Managanate?

so we use the formulas, n= m/mr and c=nv.

(acidified) iron (III) is reduced with granulated zinc
2Fe3+(aq) + Zn(s) -> 2Fe2+(aq) + Zn2+(aq)

MnO4-(aq) + 5Fe2+(aq) + 8H+(aq) " Mn2+(aq) + 5Fe3+(aq) + 4H2O(aq)

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symbolipoint
Homework Helper
Gold Member
This level of electrochemistry I understood many years ago, so I'll just trust that your equations are correct:
(acidified) iron (III) is reduced with granulated zinc
2Fe3+(aq) + Zn(s) -> 2Fe2+(aq) + Zn2+(aq)

MnO4-(aq) + 5Fe2+(aq) + 8H+(aq) " Mn2+(aq) + 5Fe3+(aq) + 4H2O(aq
Since it has been so long ago; are you sure that the presence of Zinc ion is not an interference with the titration with permanganate? You could use a table of electrochemical series to decide this. Any other advisers?

This level of electrochemistry I understood many years ago, so I'll just trust that your equations are correct:

Since it has been so long ago; are you sure that the presence of Zinc ion is not an interference with the titration with permanganate? You could use a table of electrochemical series to decide this. Any other advisers?
I think you use Zinc to reduce it to Fe2+ in order to find out the end point from that, once you titrated completely.But im not so sure :/
My lecturer told me to look up on that reaction on how to reduce it, so i should think it is that