Redox Titration Aims/Objective : To determine the molar concentration of the given KMnO4 solution.

7. Chemicals :

Oxalic dehydrate acid crystal    1.58 g

   KMnO4 solution              80 cm3

   1 M dilute sulphuric acid       80 cm3

8.  Apparatus and equipment :

9. Procedure :

1. 1.58 g of oxalic acid crystal was weighted accurately which was then dissolved in distilled water.
2. The solution was transferred to volumetric flask and made up to 250 cm3 (the mark) by distilled water.
3. 25 cm3 of oxalic acid was pipetted in a conical flask. About 25 cm3 of 1 M dilute sulphuric acid was added to it so that the solution was acidified.
4. The mixture was heated to about 60 oC by Bunsen burner.
5. The hot mixture was titrated with KMnO4 solution until the colour changed form colourless to pink.
6. Steps 3 to 5 were repeated for two more times.

10. Observations :

The colour changed from colourless to pink at the end point.

11. Data, Calculation and Results :

    Volume of titrant = (20.20 + 20.15) / 2

                  = 20.175 cm3

    Molar mass of oxalic dihydrate acid crystal
= 12 x 2 + 16 x 4 + 2 x 1 + 2(2 x 1 + 16)
= 126 g mol-1

    No. of mole of oxalic dihydrate acid crystal = 1.58 / 126
                                   = 0.0125397 mol

    Molarity of the prepared oxalic dihydrate acid solution

= 0.0125397 / (250 x 10-3)

= 0.05 M

No. of mole of potassium permanganate solution

= No. of mole of 25 cm3 of oxalic dihydrate acid solution x 2/5

= 0.05 x 25 x 10-3 x 2/5

= 5 x 10-4 mol

Molar concentration of the given KMnO4 solution = 5 x 10-4 / 20.175 x 10-3

                                             = 0.0248 M

12.  Conclusion :

     The molar concentration of the given KMnO4 solution was found to be 0.0248 M.

13.   Discussion :

1. In this redox titration, no indicator is required as the end point can be determined by the colour change of reactant (KMnO4 solution).