Estimation of dissoved oxyge (D.O.) by redox titration Flashcards
1
Q
Why was the reagent MnSO4 used?
A
Dissolved oxygen will not react completely in ts absence. Iodine is susceptible to air oxidation in an acidic medium: 4I- + 4H+ + O2 -> 2I2 + 2H2O
but this is a relatively slow reaction. The use of MnSO4 results in the formation of Mn(OH)2, which reacts completely with dissolved oxygen.
2
Q
Why is concentrated H2SO4 used?
A
To enable the Mn(IV) species to release the free iodine needed for the redox reaction.
3
Q
Why must the bottles be shaken rigorously in step 5 of the procedure?
A
To help the dissolved oxygen to react.
4
Q
Why are the bottles completely filled?
A
To prevent additional oxygen from the air dissolving in the water.
