Explain the derivation of the Iodine Clock reaction?

Answer 1

In this protocol, iodide ion is generated by the following slow reaction between the iodate and bisulfite:

IO3- (aq) + 3HSO3- (aq) → I- (aq) + 3HSO4-(aq)

This is the rate determining step. The iodate in excess will oxidize the iodide generated above to form iodine:

IO3- (aq) + 5I- (aq) + 6H+ (aq) → 3I2 + 3H2O (l)

However, the iodine is reduced immediately back to iodide by the bisulfite:

I2 (aq) + HSO3- (aq) + H2O (l) → 2I- (aq) + HSO4-(aq) + 2H+ (aq)

When the bisulphite is fully consumed, the iodine will survive (i.e., no reduction by the bisulfite) to form the dark blue complex with starch.