When potassium iodide reacts with chlorine, aqueous potassium chloride and solid iodine are formed. This chemical interaction is a classic example of a displacement reaction.
The Reaction Explained
This particular reaction occurs when chlorine gas is passed over an aqueous solution of potassium iodide. Chlorine, being more reactive than iodine, displaces the iodine from the potassium iodide compound. The result is the formation of a new salt, potassium chloride, and elemental iodine.
Why is it a Displacement Reaction?
A displacement reaction is characterized by a more reactive element taking the place of a less reactive element in a compound. In this scenario:
- Chlorine (Cl₂) is a highly reactive non-metal and a strong oxidizing agent.
- Iodine (I₂) is less reactive than chlorine.
Because chlorine has a higher reactivity than iodine, it effectively "pushes out" the iodine from potassium iodide. The iodine, which was previously in an ionic form (I⁻) within potassium iodide, is oxidized to its elemental solid form (I₂), while chlorine is reduced from its elemental form (Cl₂) to the chloride ion (Cl⁻) in potassium chloride.
Chemical Equation
The balanced chemical equation for the reaction between potassium iodide and chlorine is:
2KI(aq) + Cl₂(g) → 2KCl(aq) + I₂(s)
Here's a breakdown of the components:
| Component | State | Description |
|---|---|---|
| KI (Potassium Iodide) | Aqueous (aq) | The reactant, dissolved in water. |
| Cl₂ (Chlorine) | Gas (g) | The reactant, bubbled through the solution. |
| KCl (Potassium Chloride) | Aqueous (aq) | One of the products, remaining dissolved in water. |
| I₂ (Iodine) | Solid (s) | The other product, which precipitates out as a solid. |
This reaction demonstrates the relative reactivities of halogens, where a more reactive halogen (chlorine) can displace a less reactive halogen (iodine) from its halide salt solution.
