What is ksp in chemistry? Definition, significance, and examples

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Written by Adeel Abbas

Are you learning chemistry but don’t quite understand what is solubility product constant Ksp? Well if your answer is yes then you are on the right page. Because we are a team of chemistry professionals who are always working hard to answer your queries.

I am Adeel Abbas and I have been teaching chemistry for the last seven years. In this article, you will learn about what is solubility product Ksp in chemistry, How to solve it with the help of examples, and which factors affect it.

Definition of solubility product Ksp in chemistry

The equilibrium constant for a solid substance dissolving in an aqueous solution is the Ksp. The level at which a solute can be dissolved in the solution is represented by Ksp. The higher the Ksp value of a substance, the more it is soluble. Consider the general dissolution reaction in the solution.

aA(s) ⇌ cC(aq)+dD(aq)

The power of the concentration is equal to the coefficients of the ion and the equation to get the equilibrium. The saturated solutions of ionic compounds are described using the product constants. A saturated solution is in a state of equilibrium between the dissolved and dissociated ionic compounds. 

If you want to solve for the Ksp, it is necessary to take the concentrations of the products and multiply them. If there are coefficients in front of any of the products, it is necessary to raise the product to that coefficient’s power and also increase the concentration by that coefficient. This is shown in the picture above.

 Ksp=[C]c[D]d

The reactant, aA, is not included in the Ksp equation. Solids are not included when calculating equilibrium constant expressions because their concentrations do not change the expression; any change in their concentrations are insignificant and therefore omitted. The maximum amount of a solid that can be dissolved in the solution is represented by Ksp.

Significance of the Solubility Product

The lattice enthalpy of salt and solvation enthalpy of strontium in the solution are some of the parameters that affect the solubility of the solution. The two factors that are most important are the one and two. We can learn about the significance of the product in more detail.

  1. When a salt is dissolved in a solvent, the strong forces of attraction of solute need to be overcome by the interactions between the solute and the solvent.
  2. Energy is released during the process when the solvation enthalpy is negative.
  3. The amount of energy that is released during solvation is called solvation enthalpy.
  4. The small solvation enthalpy of non-polar solvents means that they are not enough to overcome the lattice enthalpy.
  5. The salts cannot be dissolved in non-polar solvents. In order for salt to be dissolved in a solvent, its solvation enthalpy must be greater than its lattice enthalpy.
  6. Depending on the temperature, the solubility is different for each salt.

Solved examples on How to calculate Ksc solubility product 

Example No# 1

What is the solubility product constant expression for  MgF2?

Solution

The relevant equilibrium is

MgF2(s)⇌Mg2+(aq)+2F−(aq)

so the associated equilibrium constant is Ksp=[Mg2+]−(aq) [F−]2−(aq)

Example#2

Give the solubility product constant for Ag2CrO4?

Solution

The relevant equilibrium is given by:

Ag2CrO4(s)↔2Ag+(aq)+CrO2−4(aq)

The associated equilibrium is therefore given by:

Ksp=[Ag2+]2[CrO2−4]