What is the Difference Between Ksp and Qsp?

The key difference between Ksp and Qsp lies in their definitions and the state of the solution they describe:

• Ksp (Solubility Product Constant) is a constant value that indicates the solubility of a substance in a saturated solution. It is the product of concentrations of ionic species in a saturated solution, and it is an equilibrium value.
• Qsp (Solubility Product Quotient) is a quotient used to describe the current state of an aqueous solution. It is the product of concentrations of ionic species in a solution at any given moment, and it is not an equilibrium value.

In summary:

• Ksp is the solubility product constant of a particular substance, representing the equilibrium state of a saturated solution.
• Qsp is the solubility product quotient of a solution, representing the current state of a solution, which can be unsaturated, saturated, or supersaturated.

Comparative Table: Ksp vs Qsp

The main difference between Ksp and Qsp is that Ksp represents the equilibrium constant for the dissolution of a sparingly soluble salt, while Qsp is the reaction quotient that can be used to determine the solubility of an ionic pair at a given moment in time. Here is a comparison table of the two:

In summary, Ksp is a measure of the solubility of a compound at equilibrium, while Qsp is a reaction quotient that can be used to determine the solubility of an ionic pair at a specific moment in time. Comparing Ksp and Qsp allows us to predict whether a precipitate will form when solutions of two compounds are mixed.