Prepare N/20 Mohr’s salt Solution. Using this Solution, Determine the Normality and Strength of the Given Potassium Permanganate Solution
KMnO4 is a self-indicator.
Colourless to permanent pink (KMnO4 in burette).
- Rinse and fill the burette with the given KMnO4 solution.
- 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.
- Add one test-tube (~ 20 ml) full of dilute sulphuric acid (~ 4 N) to the solution in titration flask.
- Note the initial reading of the burette.
- 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.
- Note the final reading of the burette.
- 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.