Describe the oxidizing action of potassium dichromate and write the ionic equations for its reaction with:

K2Cr2O7 ¬¬acts as a very strong oxidizing agent in acidic medium.

K2Cr2O7 gets reduced and acts as an oxidizing agent by oxidizing Iodide to iodine 

1)K2Cr2O7 oxidizes iodide to iodine 

Cr2O72-+ 14H++ 6e- --> 2Cr3+ + 7H2O

 2I- --> I2 + 2e- } x3

Overall: Cr2O72-+ 14H++ 6I- --> 2Cr3+ + 7H2O+ 3I2

2)K2Cr2O7 oxidizes iron(II) to iron(III)

Cr2O72-+ 14H++ 6e- --> 2Cr3+ + 7H2O

Fe2+ --> Fe3+ + e- } x6

Overall:  Cr2O72-+ 14H++ 6Fe2+ --> 2Cr3+ + 7H2O + 6Fe3+

3)K2Cr2O7 oxidized H2S to sulphur

Cr2O72-+ 14H++ 6e- --> 2Cr3+ + 7H2O

H2S --> S + 2H+ + 2e-} x3

Overall: Cr2O72-+ 8H++ 3H2S --> 2Cr3+ + 7H2O +3S