Ionic Product
The product of the ion concentrations actually present in a solution, each raised to its stoichiometric power.
Formula / equation
Q_sp = [A⁺]^m[B⁻]^n
Unit
Various
In depth
The ionic product is the reaction quotient for a dissolution equilibrium and can take any value, unlike Ksp which is fixed. Comparing the two tells whether the solution is unsaturated, exactly saturated or supersaturated and therefore about to precipitate.
Examples in the real world
Mixing solutions to give an ionic product of 10⁻⁸ for AgCl, well above its Ksp, produces immediate precipitation.