Determine the Percentage Composition of a Mixture of Sodium Oxalate
1   and Oxalic Acid 2 . Provided N/20 KMnO4  

Chemistry Lab ManualNCERT Solutions Class 12 Chemistry Sample Papers

Chemical Equations
determine-percentage-composition-mixture-sodium-oxalate-oxalic-acid-1

Theory
Both oxalic acid and sodium oxalate can be titrated against N/20 KMnO4 since both of them are reducing agents.
So normality (N2) of the solution will be due to both of them. From the combined normality (N2), the composition of each can be calculated.

Indicator
KMn04 is a self-indicator.

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

Procedure

  1. Rinse and fill the burette with the N/20 KMnO4, solution.
  2. Weigh exactly 1.0 g of the given mixture of oxalic acid and sodium oxalate and dissolve in water to prepare exactly 250 ml of solution using a 250 ml measuring flask. Rinse the pipette with the prepared oxalate 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. Heat the solution of titration flask to 60-70 °C and run down KMnO4 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 three concordant readings.

Observations
Normality of KMnO4 solution = 1/20
Volume of oxalate solution taken for each titration = 20.0 ml.
determine-percentage-composition-mixture-sodium-oxalate-oxalic-acid-2

Calculations
x ml of N/20 KMnO4 solution are equivalent to 20 ml of the given oxalate solution.
Applying normality equation,
determine-percentage-composition-mixture-sodium-oxalate-oxalic-acid-3