Iron content of lawn fertiliser by redox titration

[Mr.Lazy]

OK so im new to this so please excuse if im doing anything wrong

anyway ive seen many threads and posts about help with the sac questions for:

the concentration of iron(||) ions in a solution can be determined by titration against standard potassium permanganate(KMnO4) solution. In this reaction, the iron(||) ions are oxidised to iron(||) and the pomangenate ions are reduced to a solution of colourless manganese(||) ions. to design and perform a redox titration analysis to determine the iron content (as water-soluble iron(||) irons) of a lawn fertiliser. FIND: a) a half-equation for the oxidation reaction b) a half-equation for the reduction reaction c) the overall equation

and ive done this with a friend without too much trouble, but then we are asked to construct a flow chart for each step involved for the titration and write our own procedure and i have no idea at all how to do this as we only spent half a lesson being told what a redox titration is and aside from not fully understanding this we where then told to just make an experiment without further help

so if anybody can give a quick sum up of what is done that would be great or anything really, thank you 

[Panicmode]

OK so im new to this so please excuse if im doing anything wrong

anyway ive seen many threads and posts about help with the sac questions for:

the concentration of iron(||) ions in a solution can be determined by titration against standard potassium permanganate(KMnO4) solution. In this reaction, the iron(||) ions are oxidised to iron(||) and the pomangenate ions are reduced to a solution of colourless manganese(||) ions. to design and perform a redox titration analysis to determine the iron content (as water-soluble iron(||) irons) of a lawn fertiliser. FIND: a) a half-equation for the oxidation reaction b) a half-equation for the reduction reaction c) the overall equation

and ive done this with a friend without too much trouble, but then we are asked to construct a flow chart for each step involved for the titration and write our own procedure and i have no idea at all how to do this as we only spent half a lesson being told what a redox titration is and aside from not fully understanding this we where then told to just make an experiment without further help

so if anybody can give a quick sum up of what is done that would be great or anything really, thank you

Ok, this is just a simple titration experiment. You are attempting to calculate the iron content of a particular fertiliser so probably start of with something like this;

1) Dissolve g of lawn fertiliser into mL of de-ionised water. Make sure that all the fertiliser is thoroughly dissolved and filter out any insoluble particles.

2) Place this solution into the burette. Pipette a mL aliquot of Potassium permanaganate solution into a conical flask.

3) Titrate the Potassium permanganate solution with the fertiliser solution. (look for the colour change of the permangante soltuion from pruple to clear) Record the average titre.

4) Repeat steps 2 - 3 untill 3 concordant titres have been achieved.



Well, there's your experiment. As for the reactions, it's a basic redox reaction between permanganate ions and Fe(II) irons. Fe(II) is oxidised to Fe(III);

Fe²⁺ ----> Fe³⁺ + e^-

And the permangante ion is reduced to Mn²⁺

MnO₄^- +8H⁺ + 5 e^- -----> Mn²⁺ + 4H₂O


Now, for the overall equation just add the two together. I'll leave you to do that.

[Mr.Lazy]

Okay thanks alot that has help so much 

[Mr.Lazy]

I thought i had to add sulphuric acid to the fertiliser solution before it is titrated with the potassium permanganate solution, does this sound right too you?

[Panicmode]

I thought i had to add sulphuric acid to the fertiliser solution before it is titrated with the potassium permanganate solution, does this sound right too you?

Yes you're right. Excess H⁺ ions are added to acidify the solution and make sure the reaction takes place. As you can see, for the permanganate ion to be reduced, it requires 8 H⁺ ions. Therefore, sulfuric acid is added to create an acidified environment and provide the hydrogen ions to allow the reduction of the permangante ions.

Sorry, my brain was kinda frazzled cause I just woke up =D