What is the action of acidified potassium dichromate on potassium iodide `(KI) ` ?

Explanation

To determine the action of acidified potassium dichromate on potassium iodide (KI), we can follow these steps:

### Step 1: Identify the Reactants
The reactants in this reaction are potassium dichromate (K₂Cr₂O₇) and potassium iodide (KI). The potassium dichromate is acidified, typically using sulfuric acid (H₂SO₄).

### Step 2: Understand the Nature of the Reaction
Potassium dichromate is a strong oxidizing agent in acidic medium. When it reacts with potassium iodide, it oxidizes iodide ions (I⁻) to iodine (I₂) while itself being reduced.

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