# How to determine Iron concentrations in chem IA?

To determine Iron concentrations in chem IA,You can use redox titration method between the sample (fruit or vegetable extract or Iron compound)and Potassium permanganate  solution.

During the titration between your sample and KMnO4  solution the chemical reaction will take place as per following mole ratio:

5Fe2+(aq) : MnO4 (aq)

5Fe2+(aq) + MnO4 (aq) + 8H+(aq) → 5Fe3+(aq) + Mn2+(aq)

Thus with the help of standard solution of KMnO4 solution you, can calculate the concentration of Iron in your sample.

You can go through the following Sample IA of One of my student.

## Research question: To find iron (II) [Fe2+] concentration (mol/l) of the apple juices?

### Background Information:

Apple is a fruit of the domesticated tree Malus domestica. Apples vary between in each other in different aspects: acidity, shape, size, flavour and shade (red, yellow, green or mixture of colours).Mostly composed of water – 85%, carbohydrates – 13%, dietary fibre – 2% and other minerals, which includes iron.

Iron (Fe) is the transition metal of Group 8 of the periodic table.  Iron is one of the essentials minerals for the human body. It is necessary for the production of haemoglobin, a protein in the blood which carries oxygen throughout the body and required for cell growth and differentiation. Iron in apples is non-heme iron (plant iron). 100 grams of an apple contains on average 0.12 mg (moles) of iron.

Iron (Fe2+) is oxidized by potassium manganate (KMnO4) (VII) to Iron (Fe3+). By this redox titration reaction, the iron concentration of apples can be calculated. Redox reaction half equations:

MnO4 + 5Fe2+ + 8H+ -> Mn2+ + 5Fe3+ + 4H20

As seen from equation, reaction only occurs when iron(II) is present since it can be oxidized further. As a result, all of Fe3+present in apple juice must be converted to Fe2+to get proper results from the experiment: to measure total concentration of iron. Therefore, juice will be mixed with an excess of the mild reducing agent, hydroxylamine hydrochloride (NH2OH · HCl), to turn Fe3+to Fe2+ :

4Fe3+ + 2NH2OH · HCl —>  4Fe2+ + N2O + 4H+ + H2

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## 11 thoughts on “How to determine Iron concentrations in chem IA?”

1. leen says:

Hello,
I am doing something quite similar regarding how cooking tomato sauce in an iron skillet will increase the sauce’s iron content. To calculate the iron content, I was thinking of using the procedure you have described; however, I am unsure how to add the hydroxylamine hydrochloride (NH2OH · HCl) to the tomato paste to change all Fe3+ to Fe2+. In addition, after doing so, how do I titrate/know the endpoint?

1. Dr Anup Sharma says:

Dear Leen,
You can take the saturated solution of tomato sauce and add it carefully to hydroxylamine hydrochloride solution as per your trials. You can use EDTA solution for the titration and record the end point using colour change. Hope it will help you.
Stay Blessed!
All the best for your IA.

Dr Anup Sharma

2. alex says:

Would you be able to use sulphuric acid to dilute the food instead of the hydroxylamine hydrochloride solution? Also If I were to use a vegetable like spinach or peppers how would I be able to turn it into a solution thats able to use?

1. Dr Anup Sharma says:

You can use however sulphate ions can interfere.

3. Natemaneo says:

How would I change Fe3+ to Fe 2+ on vegetables

1. Dr Anup Sharma says:

Vegetable extract should be mixed with an excess of the mild reducing agent, hydroxylamine hydrochloride (NH2OH · HCl), to turn Fe3+to Fe2+
Equation: 4Fe3+ + 2NH2OH · HCl —>  4Fe2+ + N2O + 4H+ + H2

1. Natemaneo says:

Thank you
Are the states symbols correct
4Fe3+(aq) + 2NH2OH · HCL(aq) → 4Fe2+(aq) + N2O(g) + 4H+(g) + H2(g)

1. Dr Anup Sharma says:

4H+ ions are (aq).

1. Natemaneo says:

Thank you so much

4. Natemaneo says:

Also after when I titrate it how will I determine the titration like how will I know how much iron is present, do I need an indicator or something. Thanks

1. Dr Anup Sharma says:

Use the equation and stoichiometric coefficient to calculate the iron content.