Just had my examinations today.

there was a question where they asked us to perform 4 experiments

i) H2O2 + KMnO4(by drops)

ii) H2O2 + KMnO4 (by drops) + H2SO4

iii) H202 + KI

iv) H202 + KI + H2SO4

What should theoretically happen and why did the presence of H2SO4 make such a difference in outcomes?