Prepare N/20 Mohr’s salt Solution. Using this Solution, Determine the Normality and Strength of the Given Potassium Permanganate Solution

Chemical Equations

Indicator
KMnO₄ is a self-indicator.

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

Procedure

1. Rinse and fill the burette with the given KMnO₄ solution.
2. Weigh exactly 4.90 g of Mohr’s salt crystals and dissolve in water to prepare exactly 250 ml of solution using a 250 ml measuring flask. Rinse the pipette with the N/20 Mohr’s salt solution and pipette out 20.0 ml of it in a washed titration flask.
3. Add one test-tube (~ 20 ml) full of dilute sulphuric acid (~ 4 N) 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 a last single drop of KMnO₄ solution.
6. Note the final reading of the burette.
7. Repeat the above steps 4-5 times to get three concordant readings.

Observations
Normality of Mohr’s salt solution = N/20
Volume of Mohr’s salt solution taken for each titration = 20.0 ml

Calculations
(a) Normality of the KMnO₄ solution
x ml of the given KMnO₄ solution are equivalent to 20 ml of N/20 Mohr’s salt solution. Applying normality equation.

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