The Given Solution has been Prepared by Dissolving 1.6 g of an Alkali metal Permanganate per litre of Solution. Determine Volumetrically the Atomic mass of the Alkali metal. Prepare M/20 Mohr’s salt Solution for Titration

Chemical Equations
Molecular equations. Let A represent the alkali metal and AMnO4 represent alkali metal permanganate,

AMnO4 will act as a self-indicator.

End Point
Colourless to permanent pink colour (AMnO4 in burette).


  1. Weigh exactly 4.90 g of Mohr’s salt on a watch glass and dissolve in water to prepare exactly 250 ml of its solution using a 250 ml measured flask. Rinse the pipette with
    the M/20 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 AMnO4 solution.
  3. Add one test-tube (~ 20 ml) full of dilute sulphuric acid (~ 4M) to the solution in titration flask.
  4. Note the initial reading of the burette.
  5. Now add AMn04 solution from the burette till a permanent light pink colour is just imparted to the solution in the titration flask.
  6. Note the final reading of the burette.
  7. Repeat the above steps 4-5 times to get a set of three concordant readings.

Weight of watch glass =……. g
Weight of watch glass + Mohr’s salt =…………..g
Weight of Mohr’s salt = 4.90 g
Volume of solution prepared = 250 ml
Molarity of Mohr’s salt solution = M/20
Volume of Mohr’s salt solution taken for each titration = 20.0 ml

Prom the balanced chemical equation, it can be seen that 2 moles of AMnO4 react with 10 moles of Mohr’s salt.

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