Describe the oxidising action of potassium dichromate and write the io

1.	Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with:(i) iodide (ii) iron(II) solution and (iii) H2S
Answer» Potassium dichromate, in acidic medium acts as a strong oxidising agent by gaining 6e’ and forms Cr³⁺. Cr₂O₇^2- + 14H⁺ + 6e^– → 2Cr³⁺ + 7H₂O ..(1) (i) iodides 6I^– → 3I₂ + 6e^– ..(2) (1) + (2) Cr₂O₇^2- + 14 H⁺ + 6I^– → 2Cr³⁺ + 3I₂ + 7H₂O (ii) iron (II) solution 6Fe²⁺→ 6Fe³⁺ + 6e^– ..(3) (1) + (3) Cr₂O₇^2- +14H⁺+ 6Fe²⁺ → 2Cr³⁺ + 6Fe³⁺ + 7H₂O (iii) H₂S 3H₂S → 6H⁺ + 3S + 6e^– ..(4) (1) + (4) Cr₂O₇^2- +14H⁺ + 3H₂S → 6H⁺ + 3S + 2Cr³⁺ + 7H₂O

Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with:(i) iodide (ii) iron(II) solution and (iii) H2S

Answer»

Potassium dichromate, in acidic medium acts as a strong oxidising agent by gaining 6e’ and forms Cr³⁺.
Cr₂O₇^2- + 14H⁺ + 6e^– → 2Cr³⁺ + 7H₂O ..(1)

(i) iodides
6I^– → 3I₂ + 6e^– ..(2)
(1) + (2)
Cr₂O₇^2- + 14 H⁺ + 6I^– → 2Cr³⁺ + 3I₂ + 7H₂O

(ii) iron (II) solution
6Fe²⁺→ 6Fe³⁺ + 6e^– ..(3)
(1) + (3)
Cr₂O₇^2- +14H⁺+ 6Fe²⁺ → 2Cr³⁺ + 6Fe³⁺ + 7H₂O

(iii) H₂S
3H₂S → 6H⁺ + 3S + 6e^– ..(4)
(1) + (4)
Cr₂O₇^2- +14H⁺ + 3H₂S → 6H⁺ + 3S + 2Cr³⁺ + 7H₂O