Determine the percentage composition of a mixture of sodium oxalate
and oxalic acid . Provided M/100 KMnO4 solution.
KMnO4 is a self-indicator.
Colourless to permanent pink (KMnO4 in burette).
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.
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.