why do we keep insoluble salts, weak acids, weak base not in ion form when writing net ionic equation but do show them separate when we are just talking about the substance

Question

for example AgCl is insoluble salt but would write it as AgCl <-> Ag+ +Cl- in equation form , however would just keep it as AgCl in a net ionic equation.

Answer 1

The separation of insoluble salts, weak acids and weak basis into ions is so very small that we generally do not show them as ionizing or dissociating. If you were to write the net ionic equation for the formation of AgCl, it would be...

Ag⁺(aq) + Cl^-(aq) ==> AgCl(s)

If you were to write the Ksp expression for AgCl, it would be ...

AgCl(s) ==> Ag⁺(aq) + Cl^-(aq)

But considering the Ksp is on the order of 10^-10, you can see that a very small percentage of the AgCl is in the form of Ag⁺ and Cl^-. This is why we leave it as AgCl(s) in the net ionic equation. Same holds true for weak acids, bases, and other weak electrolytes.

Hope this answers your question satisfactorily. If not, please leave a comment and will try to explain further.