Prepare a Solution of Ferrous Ammonium Sulphate Containing Exactly 17.0 g of the Salt in one Litre

Prepare a Solution of Ferrous Ammonium Sulphate (Mohr’s salt) Containing Exactly 17.0 g of the Salt in one litre. With the help of this Solution, Determine the Molarity and the Concentration of KMnO₄ in the Given Solution

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Chemical Equations

Indicator
KMnO₄ is a self-indicator.

End Point
Colourless to permanent pink colour (KMnO₄ in burette).

Procedure
1. Weigh exactly 4.250 g of Mohr’s salt on a watch glass and dissolve in water to prepare exactly 250 ml of solution with the help of a 250 ml measuring flask. Rinse the pipette with the prepared Mohr’s salt solution and pipette out 20.0 ml of it in a washed titration flask.
2. Rinse and fill the burette with the given KMnO₄ solution.
3. Add one test-tube (~ 20 ml) full of dilute sulphuric acid (~ 2 M) to the solution in titration flask.
4. Note the initial reading of the burette.
5. Now add KMnO₄ solution from the burette till a permanent light pink colour is imparted to the solution in the titration flask on addition of last single drop of KMnO₄ solution.
6. Note the final reading of the burette.
7. Repeat the above steps 4-5 times to get a set of three concordant readings.

Observations
Weight of watch glass =……. g
Weight of watch glass + Mohr’s salt =…………..g
Weight of Mohr’s salt = 4.250 g
Volume of Mohr’s salt solution prepared = 250 ml
Volume of Mohr’s salt solution taken for each titration = 20.0 ml

Calculations
Concentration of Mohr’s salt, ferrous ammonium sulphate, FeSO₄.(NH₄)₂ SO₄.6H₂0 in the prepared solution = 17.0 g/litre.

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