What do you observe when `HgCl_2` and KI rubbed in mortar.

Explanation

To solve the question, "What do you observe when `HgCl_2` and KI are rubbed in mortar?", we will follow these steps:

### Step 1: Identify the Reactants
The reactants in this reaction are mercuric chloride (HgCl₂) and potassium iodide (KI).

### Step 2: Understand the Reaction
When HgCl₂ and KI are rubbed together, a chemical reaction occurs. The mercuric chloride reacts with potassium iodide to form mercuric iodide (HgI₂) and potassium chloride (KCl).

...