Answer:
1. iodide ion into neutral iodine
2. blue-black
3. neutral iodine into iodide ion
4. clear
Explanation:
The function of hypochlorite in iodine titration is to oxidize the iodide ion into iodine molecule as shown below;
ClO-(aq) + 2H+(aq) + 2I-(aq) ---------> 6 I2(l) + Cl- (aq)+ H2O(l)
The addition of starch to iodine leads to the formation of a starch iodide complex which has a blue black colour.
the titrant, thiosulfate, reduces neutral iodine into iodide ion as shown below;
I2 + 2S2O32- → 2I- + S4O62-
At end point, the solution becomes clear again.