Question

What is the difference between \[Qsp\] and \[Ksp\] ?

Answer 1

Hint: We know that the solubility product constant is a simplified equilibrium constant which is denoted as \[Ksp.\] It is defined for the equilibrium between a solid and its respective ions in a given solution. It is the equilibrium constant for a solid substance dissolving in an aqueous solution. It represents the level at which a solute dissolves in solution.

Complete answer:
Solubility is defined as the property of a substance known as solute to get dissolved in a solvent for the formation of a solution. The solubility of ionic compounds that dissociate and form cations and anions in water vary to a great extent. The solubility product constant is used to describe the saturated solutions of ionic compounds having relatively low solubility. A saturated solution is said to be in a state of dynamic equilibrium between the ionic compound and the undissolved solid.
Solubility is the maximum possible concentration of a solute in a solution at a given temperature and pressure. We can determine the solubility product of a slightly soluble form the measure of its solubility at a given temperature and pressure, provided that the only significant reaction that occurs when the solid dissolves is its dissociation into solvated ions.
\[Q,\] the so-called ion product, is a TRANSIENT, non-equilibrium value. For a sparingly soluble salt, \[MXn,\] certainly we can measure a constant for the equilibrium reaction for a given temperature: \[MX{{n}_{\left( s \right)}}\rightleftharpoons M{{n}^{+}}+n{{X}^{-}}\]
And \[Ksp=\left[ M{{n}^{+}} \right]{{\left[ {{X}^{-}} \right]}^{n}}\]
And likewise we so define \[Q=\left[ M{{n}^{+}} \right]{{\left[ {{X}^{-}} \right]}^{n}}.\]
If \[Q=Ksp,\] then equilibrium has been reached, and no MACROSCOPIC change will occur. If \[\text{QKsp},\] then precipitation will occur.

Note:
Remember that the solubility product is always dependent upon the solubility equation. The solubility equation depends upon the concentration of the dissociated ions and their numbers. The solubility product constant describes the equilibrium between a solid and its constituent ions in a solution.