1. Why does H2O2 and dish soap react ? 2. Why does potassium iodide consider as a catalyst for this reaction ?

Answer 1

As I pointed out in another one of your questions on the same subject, the catalyzed decomposition of H2O2 takes place in 2 steps:

H₂O₂ (aq) + I^- (aq) ==> H₂O (l) + OI^- (aq) 

H₂O₂ (aq) + OI^- (aq) ==> H₂O (l) + O2 (g) + I^- (aq)

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2H₂O(aq) + I^-(aq) ==> 2H₂O(l) + O₂(g) + I^-(aq) Overall reaction

NOTE that the Iodide ion (I-) is not used up (it is regenerated), so it qualifies as a catalyst.

Answer 2

1. Why does H2O2 and dish soap react ?

I don't think they do react chemically together. I think 2H2O2→ 2 H2O + O2

This reaction is spontaneous.

2. Why does potassium iodide consider as a catalyst for this reaction ?

Because the KI accelerates the decomposition of H2O2, but does not combine with the reactant chemically or produce new products.