To determine the Molarity of KMnO4 solution by titrating it against a standard solution of oxalic acid. (M/20 oxalic acid solution).

 

To determine the Molarity of KMnO4   solution 

by titrating it against a standard solution of 

oxalic acid. (M/20 oxalic acid solution).

Experiment – 2

Class – XII

Subject – Chemistry

Aim:-

To determine the Molarity of KMnO₄   solution by titrating it against a standard solution of oxalic acid. (M/20 oxalic acid solution).

Theory:-

The reaction between oxalic acid and KMnO₄ in acidic medium is a redox reaction as oxalic acid in acidic medium is a good reducing agent and KMnO₄ in acidic medium is a good oxidizing agent.

The reactions can be written as:

Apparatus Required :-

Burette, Burette Stand, Pipette, Titration flask, Test tube, Funnel, Beaker, Burette etc.

Chemical Required:-

Oxalic acid crystals, distilled water, Sulphuric acid  etc.

Procedure:-

            1.57 g of oxalic acid crystals was it on the analytical balance.

      ii.            250 ml of M/20 oxalic acid solution was prepared by sissolving 1.57 g of oxalic acid in     water and 250 ml of it was pipetted out in a clean titration flack.

    iii.            The Burette was filled and rinsed with the given KMnO₄ solution.

   iv.            One test tube full of dil. H₂SO₄ was added to the solution in titration flask.

     v.            The initial reading of burette was noted.

   vi.            The flask was heated to b0 – 70’C.

 vii.            KMnO₄ solution was added from the burette to the titration flask till a permanent light pink color was imported to the solution in the titration flask.

viii.            The final reading of the burette was noted.

    ix.            The above steps were repeated till two concordant volume of KMnO₄ were recorded.

Observation :-

            Weight of watch glass = ……………..gms

            Weight of watch glass + oxalic acid = ……………… gms

            Weight of oxalic acid = 0.63 gms

            Volume of solution prepared = 250 ml

            Molarity of solution = M/20

            Volume of solution taken for each titration = 20 ml

S.No.	Initial Reading of burette (R1)	Final reading of burette (R2)	Volume of KMnO4  Solution used (R1 +R2)
1.	0	19.3 ml	19.3 ml
2.	0	17.5 ml	17.5 ml
3.	0	17.5 ml	17.5 ml
Final Reading			17.5 ml

 

Calculation:-

From the balanced chemical Redox equations, it is clear that 1 moles of KMnO₄ reacts with 5 moles of oxalic acid.

A.    Determination of molarity of KMnO₄  solution:

B.    Determination of strength of KMnO₄  solution:

Strength = Molarity X molecular mass of KMnO₄

0.02 x 158 = 3.16

Result:-

The molarity and strength of given KMnO₄   solution is.

Precaution:-

1.     Transfer the oxalic acid crystals from the watch glass to the beaker carefully, so the not even a single crystal is lost.

2.     Read upper meniscus in the burette as KMnO₄  solution is highly coloured solution.

3.     Do not rinse titration flask with oxalic acid solution.

4.     Oxalic acid solution should not be heated beyond 70’C.

5.     Oxalic acid solution should keep warm during titration.

S. No.	Name of Experiment	Link
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