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

Chemical Equations

KMnO4 is a self-indicator.

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


  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.

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

(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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