When chlorine gas is added to a potassium iodide solution, a reddish-brown solution is formed, and iodine is liberated. This is a classic example of a halogen displacement reaction.

Here's the breakdown:

* Reaction:

Cl₂(g) + 2KI(aq) → 2KCl(aq) + I₂(aq)

* Explanation:

* Chlorine (Cl₂) is a more reactive halogen than iodine (I₂).

* Chlorine displaces iodine from its compound, potassium iodide (KI), forming potassium chloride (KCl) and elemental iodine (I₂).

* Iodine is sparingly soluble in water and gives the solution a reddish-brown color.

Observations:

* The solution changes color from colorless to reddish-brown.

* A pungent odor of chlorine gas might be detected initially.

Safety:

* Chlorine gas is toxic and should be handled with care in a well-ventilated area.

* Iodine is also toxic and should be handled with caution.

Additional points:

* The reaction is exothermic and releases heat.

* The reaction can be used to prepare iodine in the laboratory.

* This type of reaction is common for halogens, with a more reactive halogen displacing a less reactive one.