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

Chemistry Lab ManualNCERT Solutions Class 12 Chemistry Sample Papers

Chemical Equations

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.

Calculations

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