The insoluble salt that forms when you mix silver nitrate (AgNO₃) with potassium chloride (KCl) is silver chloride (AgCl).

Here's the chemical reaction:

AgNO₃ (aq) + KCl (aq) → AgCl (s) + KNO₃ (aq)

* AgNO₃ (aq): Silver nitrate, dissolved in water (aqueous solution)

* KCl (aq): Potassium chloride, dissolved in water (aqueous solution)

* AgCl (s): Silver chloride, a white solid precipitate (insoluble in water)

* KNO₃ (aq): Potassium nitrate, remains dissolved in water (aqueous solution)

This reaction is a classic example of a precipitation reaction, where two soluble salts react to form an insoluble salt (precipitate).