Question

When determining the amount of an oxidant present by titration, you can use iodine and starch as an indicator.

Answer 1

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.