[soy matcha latte]

Hi guys! I'm currently writing the analysis part of my titration coursework. However I'm finding it hard to explain how I obtained 104.3 mg Fe2+ content when it says 14mg on the label. Its ferrous fumarate tablets against potassium permanganate.

Please don't say I've calculated it wrong because I have repeated the Fe content calculation so many times and I am 100% correct! I am not going crazy!!
I would appreciate if you guys can tell me what to look for and the other factors that may have affected this, my brain is exhausted I need new eyes and brain!

[Corribus]

It's very hard to explain anything since you haven't provided any information about what you're doing or how you did it, much less any actual calculations.

[soy matcha latte]

I had to calculate the Fe2+ content of iron tablets and capsules. I've done the analysis for the capsules so this is just for the tablets.

SO I used 2 tablets. Total mass of these two is 0.54g.

I used 0.005 M potassium permanganate (this is the burette content). Prior to titration, I had to crush the tablets and add 100cm3 of 1 M sulfuric acid. Transfer to a 250cm3 volumetric flask. Use deionised water to fill up to the graduation line. Transfer this to a conical flask using a 25cm3 pipette, then add excess 10cm3 sulphuric acid (the same one used a while ago). Got an average titre of 14.9cm3. Did the calculations..

5Fe2+ + MnO4- + 8H+ ---> Mn2+ + 5Fe3+ + 4H2O

I found the moles of the potassium permanagante, used the above equation to use the ratio, multiplied the moles of potassium permanganate by 5 to get the moles of Fe2+. Then divided it by 10 to get the moles of Fe2+ in the 250 volumetric flask (as I used 25cm3 glass pipette to transfer the solution to the conical flask).

I then calculated for the mass using the rfm of iron by multiplying the calculated moles by 56. The mass is divided by two (as I used two tablets). then I converted it to mg by multiplying by 1000.

Why is the value so big.

[soy matcha latte]

It's very hard to explain anything since you haven't provided any information about what you're doing or how you did it, much less any actual calculations.

I've posted a more detailed explanation; please help;

[Borek]

Then divided it by 10 to get the moles of Fe2+ in the 250 volumetric flask (as I used 25cm3 glass pipette to transfer the solution to the conical flask).

Actually you should multiply, not divide. Yes, it makes the result even worse.

Other than that your calculations look OK. No idea why the discrepancy.

[Borek]

As it was hinted at in the other thread, fumaric acid is a candidate for being oxidized as well, giving a potentially huge positive error.

[soy matcha latte]

But how? I'm estimating the Fe2+ content. How will fumaric acid affect this redox reaction and increase the iron yield?

[Borek]

You are calculating amount of Fe²⁺ assuming it reacted stoichiometrically with the permanganate. What if permanganate oxidizes something present in the solution? Does the amount of permanganate used still reflect the amount of Fe²⁺?

[soy matcha latte]

You absolute legend. I've just finished my analysis, thank you! Definitely needed fresh eyes and brain.