Ammoniacal silver nitrate is a solution, not a single compound with a fixed chemical formula. It's formed when silver nitrate (AgNO3) reacts with ammonia (NH3).

Here's what happens:

1. Formation of the diamminesilver(I) ion: Silver ions (Ag+) react with ammonia to form the diamminesilver(I) ion, [Ag(NH3)2]+. This reaction is reversible and depends on the concentration of ammonia.

2. Solution formation: The diamminesilver(I) ion remains in solution along with nitrate ions (NO3-) from the original silver nitrate.

Therefore, there isn't a single, fixed chemical formula for ammoniacal silver nitrate. It's best described as a solution containing [Ag(NH3)2]+ and NO3- ions in varying amounts depending on the conditions.