Introduction 

 A Solution is a liquid that contains one or more solutes and a solvent in a homogenous mixture. Sugar cubes in a cup of tea or coffee are a common example of a solution. Solubility refers to the ability of sugar molecules to dissolve. As a result, the solubility of sparingly soluble salts can be defined as the ability of a material (solute) to dissolve in a specific solvent. When dissolved in a solvent, a solute is any solid, liquid, or gas material. Sparingly soluble salt examples include acetate, ammonium, sodium and potassium salts, any chlorides, bromides, etc.

Characteristics of Physical Changes:

• It is a one-time adjustment.
• It only affects the substance’s physical qualities, such as shape and size.
• It involves very little to no energy absorption.
• Physical changes do not usually necessitate the creation of energy.
• There is no new substance generated.

Characteristics of Chemical Changes in Sparingly Soluble Salts:

• It is a long-term change.
• It can alter a substance’s physical and chemical properties and composition.
• The process of energy absorption and evolution takes place.
• Most of the time, it entails the generation of energy.
• It always comes with one or more new substance(s).
• A solute is a substance that dissolves in a solvent to generate a homogenous mixture.

Factors Affecting Solubility:

Solubility refers to the maximum amount of solute that can be dissolved in each amount of solvent at a given temperature. The elements that influence solubility differ based on the solute’s state and can be classified as follows:

1. Liquid Solubility in Liquid:

Solutes are characterized as highly soluble, sparingly soluble salts, or insoluble depending on the concentration of solute dissolved in a solvent. It is soluble if more than 0.1 g of solute can be dissolved in 100 ml of solvent. It is deemed sparingly soluble if it is less than 0.1 g. A saturated solution is when a specific amount of solute is soluble in a solvent at a specific temperature. In contrast, a supersaturated solution is when the solute begins to precipitate at a specific concentration at the same temperature. Some of the elements that determine solubility are as follows:

Temperature: In the case of solids and liquids, solubility increases with temperature, whereas in the case of gases, it decreases with temperature.

Force: Forces differ depending on the intermolecular forces and bonds present. As a result, like dissolves like, whereas dissolving unlike substances is difficult.

Pressure: As partial pressure in gases rises, solubility rises as well.

2. Liquid solubility of solids:

When a solid solute is given to a solvent, the dissolution process causes the solute particles to dissolve in the solvent. Between these two processes, a state of dynamic equilibrium is established. At this point, the number of solute molecules entering the solution equals the number of particles leaving the solution, resulting in a constant concentration of the solute in the solution at a given temperature and pressure. The subsequent factors influence solubility:

Temperature Effect: If the dissolution process is endothermic, solubility increases with increasing temperature; if the process is exothermic, solubility decreases with increasing temperature.

Pressure Changes Have Little Impact: A change in pressure has little impact.

3. Gas solubility in liquids:

This idea is about a gas dissolving in a solvent. Temperature and pressure and the composition of the solute and the solvent have a significant impact on gas solubility in liquids.

Pressure: As pressure rises, solubility rises as well. Henry’s Law establishes a quantitative relationship between pressure and gas solubility in a liquid.

Temperature: As the temperature rises, the solubility of gases in liquids decreases. 

The solubility of sparingly soluble salt is given by the equation:-

S = K× ΛM.

To confirm Le Chatelier’s Principle, since dissolution is an exothermic process, the solubility should decrease as the temperature rises.

Solubility and the Common Ion Effect:

According to the solubility product expression, the equilibrium concentrations of the cation and anion are inversely linked. That is, as the anion concentration rises, the maximum cation concentration required for precipitation falls and vice versa so that Ksp remains constant. As a result, an ionic compound’s solubility is determined by the quantities of other salts containing the same ions. The production of complex ions is one of the exceptions, which will be explored later. Also, the hydration energy of sodium sulfate is soluble in water, whereas barium sulfate is only sparingly soluble. When the hydration energy exceeds the lattice energy, the salt dissolves in water and vice versa.

Product Constant of Solubility in Sparingly Soluble Salts:

Solubilities of ionic substances vary greatly. At 25°C, sodium chloride dissolves in around 360 g per liter of water. Alkali metal salts are usually quite soluble. On the other hand, zinc hydroxide has a solubility of just 4.2 10-4 g/L of water at the same temperature. Many hydroxide-containing ionic compounds are relatively insoluble.

Even though most ionic compounds are considered insoluble, they will dissolve to some amount in water. Since whatever fraction of the chemical that dissolves also dissociates, these “largely insoluble” compounds are termed strong electrolytes. When silver chloride is introduced to water, it dissociates to a minor extent into silver ions and chloride ions.

AgCl (s)  ⇄   Ag+ (aq)  +  Cl− (aq)

Because the dissociation occurs at a modest level, the process is represented as an equilibrium. As a result, an equilibrium expression for the process can be written. Keep in mind that the concentration of solid silver chloride is constant; hence it is not included in the equation.

Ksp = [Ag+] [Cl−]

The solubility product (Ksp) is used to compute equilibrium ion concentrations in the solution, whereas the ion product (Q) is used to characterize concentrations that aren’t always at equilibrium. The solubility product (Ksp) and the equilibrium constant for a dissolution reaction, measure a compound’s solubility. Ksp is described in terms of the molar concentrations of the component ions, whereas solubility is normally represented in terms of the mass of solute per 100 mL of solvent. The ion product (Q), on the other hand, describes concentrations that aren’t necessarily equilibrium. When two soluble salt solutions are mixed, we may determine if a precipitate will develop by comparing Q and Ksp. In a sparingly soluble salt solution, adding a common cation or common anion affects the solubility equilibrium in the direction Le Chatelier’s principle anticipated.

Conclusion:

In a saturated solution, there is a dynamic equilibrium between the excess solute and the ions furnished by that part of the solute that has gone in the result. As a general rule, a salt can dissolve in a certain solvent if its solvation enthalpy is greater than its lattice enthalpy so that the latter can be exceeded by the former. This is because every salt gets its characteristic solubility, which is temperature-dependent.