Question

What is the reagent of the clock reaction? (The reagent whose concentration is a fixed value throughout the experiment.) O iodide ion, I thiosulfate ion, so O starch O peroxydisulfate ion, ,0 The starch indicator reacts with to form the dark blue complex which signals the end of the clock reaction. 9,03 NO;

Answer 1

Ans 1 : thiosulfate ion, S₂O₃^2-

In the clock reaction , the sulfuric acid is present in the solution alongwith H2O2. To this solution sodium thiosulfate is added alongwith potassium iodide and starch.

Thiosulfate ion converts the each triiodide ion into iodide ions.

Ans 2 : I₃^-

The starch indicator reacts with I₃^- to form the dark blue complex which signals the end of reaction.

First the peroxide converts the iodide ion into triiodide , then this triiodide ion is converted into iodide ion by thiosulfate ion.