Determine the percentage composition of a mixture of  sodium oxalate
1   and oxalic acid 2. Provided M/100 KMnO4  solution.

Chemistry Lab ManualNCERT Solutions Class 12 Chemistry Sample Papers

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

Indicator
KMnO4 is a self-indicator.

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

Procedure
1. Weigh exactly 1.0 g of the given mixture of sodium oxalate and oxalic acid and dissolve in water to prepare exactly 250 ml of solution using a 250 ml measuring flask. Rinse the pipette with the given oxalate solution and pipette out 20.0 ml of it in a washed titration flask.
2. Rinse and fill the burette with the KMnO4. solution.
3. Add one test-tube (~ 20 ml) full of dilute sulphuric acid (- 2 M) 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 imparted to the solution in the titration flask on addition of a last single drop of KMnO4 solution.
6. Note the final reading of the burette.
7. Repeat the above steps 4—5 times to get three concordant reading.

Observations
Weight of watch glass =……. g
Weight of watch glass + Mohr’s salt =…………..g
Weight of mixture = 1.0 g
Volume of solution prepared = 250 ml
Molarity of KMnO4 solution =1/100
Volume of oxalate solution taken for each titration = 20.0 ml.
determine-percentage-composition-mixture-sodium-oxalate-oxalic-acid-2

Calculations
determine-percentage-composition-mixture-sodium-oxalate-oxalic-acid-3
determine-percentage-composition-mixture-sodium-oxalate-oxalic-acid-4