The estimation of iron(II) and iron(III) in a mixture containing both
Iron is a transition element. A transition element is an element that forms at least one ion with a partially file d orbital1. Transition metals have several different oxidation states, so can be oxidized and reduced.
Oxidizing the Fe2+ will make it Fe3+, and it will lose an electron.
Fe3+ e- + Fe3+
Reducing Fe3+ will bring it back to Fe2+, as it will gain an electron.
Fe3+ + e- - Fe2+
I have been given a solution containing between 1.1g and 1.3g of iron ions, a mixture of Fe2+ and Fe3+. To work out how much Iron(II) and Iron(III) is in the mixture, I will start with a titration. I will determine the amount of Fe2+ in the mixture originally by titrating with potassium permanganate, and therefore oxidising the Fe2+ to Fe3+. Potassium permanganate, KMnO4, is self indicating, so when the oxidation point is reached, it changes brown. Then I will reduce the Fe3+ back to Fe2+ with zinc powder and work out the amount of Fe2+ in the remaining mixture by titrating the new mixture against approximately 0.1 molar potassium permanganate.
Then Fe2+ mass in 2nd solution – Fe2+ mass in 1st solution = Mass of Fe2+ originally in the solution.
This experiment will only give me the Mass of Fe2+ in the solution, so the Fe3+ will need to be worked out by subtracting the Mass off the Fe2+ from the 200cm3 solution used at the beginning.
Manganate to iron is a 1:5 ratio. The concentration of manganate at any time is 5 x less than Fe2+. 2
