Pb(NO3)2 +KI = PbI2 +KNO3

what is the observation?

Lead nitrate is white in colour, and its aqueous solution is colourless. When solutions of lead nitrate and potassium iodide are mixed together, then a yellow precipitate of lead iodide is formed. Following is the chemical equation for the reaction

2KI (aq) + Pb(NO₃)₂ )aq) → PbI₂ (↓) + 2 KNO₃ (aq)