**You are Provided with a Partially Oxidised Sample of Ferrous Sulphate (FeSO**_{4}.7H_{2}0) Crystals. Prepare a Solution by Dissolving 14.0 g of these Crystals per litre and Determine the Percentage Oxidation of the given Sample. Given M/100 KMnO_{4} Solution

_{4}.7H

_{2}0) Crystals. Prepare a Solution by Dissolving 14.0 g of these Crystals per litre and Determine the Percentage Oxidation of the given Sample. Given M/100 KMnO

_{4}Solution

**Chemical Equations**

**Theory**

Since the given sample contains partially oxidized ferrous sulphate, it contains both ferrous ions, Fe^{2+} (unoxidised) and ferric ions Fe^{3+} (oxidised). The strength of partially oxidised sample is known. The solution of partially oxidised FeSO_{4} of known strength is titrated against standard KMnO_{4} solution to determine the molarity and strength of the unoxidised ferrous sulphate. From this the percentage oxidation of the sample can be calculated.

**Indicator**

KMnO_{4} is a self-indicator.

**End Point**

Colourless to permanent pink (KMnO_{4} in burette).

**Procedure**

- Weigh exactly 3.50 g of the given sample of ferrous sulphate on a watch glass and dissolve in water to prepare exactly 250 ml of solution using a 250 ml measuring flask. Rinse and fill the pipette with prepared ferrous sulphate solution and pipette out 20.0 ml of it in a washed titration flask.
- Rinse and fill the burette with the M/100 KMnO
_{4}solution. - Add one test-tube (~ 20 ml) full of dilute sulphuric acid (- 2 M) to the solution in titration flask.
- Note the initial reading of the burette.
- Now add KMnO
_{4}solution from the burette till a permanent light pink colour is imparted to the solution in the titration flask on addition of a last single drop of KMnO_{4}solution. - Note the final reading of the burette.
- Repeat the above steps 4—5 times to get three concordant reading.

**Observations**

Weight of watch glass =……. g

Weight of watch glass + Mohr’s salt =…………..g

Weight of mixture = 3.50 g

Volume of solution prepared = 250 ml

Molarity of KMnO_{4} solution =M/100

Volume of oxalate solution taken for each titration = 20.0 ml.

**Calculations**

Molarity of the standard KMnO_{4} solution = M/100