Principle :
MnO4- & Fe2+ react according to the equation in the presence of H2SO4 .
2KMnO4 + 10FeSO4 + 8H2SO4 → K2SO4 + 2MnSO4 +5Fe2(SO4)3 + 8H2O
Fe 2+ - e - → Fe 3+ ( Oxidation )
5 Fe 2+ - 5 e - →5 Fe 3+ ( Oxidation )
MnO4- + 5e - → Mn 2+ ( Reduction )
In acid medium KMnO4 react as an Oxidant and Fe2+ reducing agent / reductant . Fe2+ reacts with KMnO4 as reducing agent. So Fe2+ is Oxidized to Fe3+ and MnO4- is reduced to Mn2+ .
Apparatus : Digital balance, Measuring flask, Wash bottle, Conical flask, pipette, Burette, Stand, and Cramps .
Chemical : Ferrous Sulphate , Sulphuric Acid , Potassium Permanganate .
Preparation of Standard (potassium permanganate) Solution:
Molecular Weight of KMnO4 = 158.03
Equivalent Weight of KMnO4= 158.03/5
= 31.606
1000 ml 1N solution KMnO4 present =31.606 g
100 ml 0.1N solution KMnO4 present = 31.606 x 100 x 0.1 / 1000
= 0.31606 g
Concentration of KMnO4 = 0.31606 /0.31606 x 0.1 N
= 0.1 N
Procedure:
1. By taking weight 0.31606g KMnO4 and transfer to 100 ml measuring flask. Dissolve it in distilled water and made up to the mark. Shake well and mixed thoroughly.
2. We took clean burette rinsed and then filled it with KMnO4 solution. Then the burette was stood by stand and cramps.
3. We took a pipette of 10 ml which was cleaned and washed with distilled water and then ringed with FeSO4 solution.
4. Took 10ml solution of FeSO4 in a conical flask from the measuring flask (Beaker if the solution pours in the beaker) with the help of an appropriate pipette.
5. Added 20ml H2SO4 & diluted with a little of water.
6. This experiment there was no needed to add extra indicator because KMnO4 itself acts as an indicator.
7. Place the burette such way that its tip 1 inch up from the mouth of the conical flask. But do not touch it.
8. Noted the burette reading.
9. Slowly run the KMnO4 solution in to the FeSO4 solution and continuously rotated the conical flask. But not touch with the tip of the burette.
10. Add slowly until the solution comes colorless to light pink colors. This is the end point of the titration.
11. Noted the burette reading in the data table.
12. The difference between the initial and final burette reading gives the volume of the KMnO4 solution required to completely neutralize 10 ml of FeSO4 solution.
13. The procedure is repeated three or four times.
Table: Determination volume of KMnO4
Calculation:
1000 ml 1 N KMnO4 reacts with = 55.85 g Fe2+ ion
1ml… …. 1 N… ….. … …. ….. ….. … = 55.85/1000 g Fe2+ ion
X ml…. ….0.1 N…. ….. …. …… …… =55.85 * X * 0.1/ 1000
= Y g Fe2+ ion
In 10ml sample solution Fe2+ present = Y g
1000 ml ….. …… ….. … ….. ….. …… ….=Y * 1000 /10 ml
= Z g
Result:
No of Fe2+ ion present in solution …. …. …. g/L