Describe the oxidising action of potassium dichromate and write the ionic equations of reaction with:
(i). Iodide
(ii). Iron (II) solution and
(III). `H_2S`

Explanation

### Step-by-Step Solution:

**1. Understanding the Oxidizing Action of Potassium Dichromate:**
- Potassium dichromate (K₂Cr₂O₇) is a strong oxidizing agent. An oxidizing agent is a substance that gains electrons in a chemical reaction and, in doing so, causes another substance to be oxidized (lose electrons). During this process, the oxidizing agent itself is reduced.

**2. Reaction with Iodide (I⁻):**
- When potassium dichromate reacts with potassium iodide (KI), it oxidizes iodide ions (I⁻) to iodine (I₂).
- The balanced ionic equation for this reaction is:
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