When a solution of potassium iodide is added to a solution of lead nitrate in a test tube. a reaction takesplace.

When potassium iodide (KI) is added to lead(II) nitrate (Pb(NO₃)₂) in a test tube, a reaction occurs that results in the formation of lead(II) iodide (PbI₂), which is a bright yellow precipitate, and potassium nitrate (KNO₃) in solution. This reaction is a classic example of a double displacement (or metathesis) reaction.

Chemical Reaction

1. Reactants:

   • Potassium iodide (KI)
   • Lead(II) nitrate (Pb(NO₃)₂)

2. Products:

   • Lead(II) iodide (PbI₂) (precipitate)
   • Potassium nitrate (KNO₃) (aqueous)

Balanced Chemical Equation

The balanced chemical equation for this reaction is:

2 \text{KI}_{(aq)} + \text{Pb(NO}_3\text{)}_{2(aq)} \rightarrow \text{PbI}_2_{(s)} + 2 \text{KNO}_3_{(aq)}

Observations

• Upon mixing these two solutions, a bright yellow precipitate of lead(II) iodide forms instantly, indicating that a chemical reaction has taken place.
• The potassium nitrate remains in the solution, as it is soluble in water.

This demonstration is often used in educational settings to illustrate concepts such as solubility, precipitation, and chemical reactions. The formation of lead(II) iodide is particularly striking due to its vivid color and is a clear visual indication of the reaction.