Solubility Formula

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What is Solubility Formula?

When a solid substance is dissolved in a liquid, then both the substance combine to form an aqueous solution, this phenomenon or the property of the liquid is known as Solubility. The Solubility product constant is nothing but the equilibrium constant of the process of dissolution of the substance that is in a solid or liquid state to an aqueous solution. The Solubility Formula or the Solubility product Formula for the liquid is denoted by the symbol Ksp. Thus, Solubility can be properly defined as a property of the substance called the solute for getting dissolved in a solvent for the formation of a solution. It is one of the physical characteristics of the compounds. Let’s take an example, the Solubility of the ionic compound, which usually dissociates into cations and anions, in water varies to a great extent. Some compounds are highly soluble such that they may even absorb moisture from the atmosphere while on the other hand, some are highly insoluble.

The Solubility Product

The Solubility of a substance depends on a number of factors. So, let us try and understand the process of Solubility which works:

  • Whenever a particular salt is dissolved in a solvent, the ionic forces of attraction (the lattice enthalpy of the ions) within the solute are overcome by the interactive forces in-between the ions and the solvent for the solute to dissolve in the solvent. 

  • So, whenever the solute dissolves in the solvent, typically some energy is released in the process, and hence, the solvation enthalpy of the ions becomes negative. 

  • The nature of the solvent is determined by the amount of energy that is released during the process of solvation giving the solvation enthalpy.

  • In the case of the non-polar solvents, the energy is not sufficient to overcome the forces between the components of the solute i.e. the lattice enthalpy, and hence, in turn, non-polar solvents have very low solvation enthalpy.

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FAQs (Frequently Asked Questions)

1. What is the Difference Between Solubility and Solubility Product Constant?

The solubility of a given solute in a given solvent is given by the total amount of the solute that can be dissolved in the solvent at equilibrium. On the other hand, the solubility product constant is an expression, an equilibrium constant that provides the information at the equilibrium between the solute and the constituent ions that it dissociated into inside the solution. It is important to determine the concentration of the solute in the solvent when a substance has been dissolved to determine how much more can be dissolved in the solvent.

2. What are the factors that affect the solubility constant?

Some of the factors that have or can have an impact on the solubility constant include, the common-ion effect which is the presence of a common ion which can lead to lowering solubility and hence lowering the value of the solubility product. Another factor is the diverse-ion effect in which if the ions in the solutes are uncommon, then the value of the solubility product is high. Another factor that plays a role in affecting the value of solubility products is the presence of ion pairs.

3. Is water a good solvent?

Water is a polar molecule, it has one oxygen and two hydrogen atoms. As the oxygen atom has much more tendency to draw electrons and due to being in the sp3 hybridization, there is the development of a polar charge inside the water molecule which is positive at the hydrogen atom and negative at the oxygen atom, so this makes Water a highly polar molecule and a very good solvent. Many acids and chemicals are stored by making a solution with Water.

4. Why does Common Salt dissolve in water?

Common salt or sodium chloride as it is scientifically known is very easily dissolved in water because as soon as salt is inserted into water, there is the development of cations and anions inside the salt molecule because sodium positive ion and chloride negative anion is very stable ions and hence there is a tendency to dissolve into these ions. And as water is a polar solvent, the lattice energy is easily met.

5. I am having trouble while solving the questions of Solubility, what shall I do?

Solubility is the part of inorganic chemistry which is one of the most important subjects in the JEE examinations, there are a large number of questions that are asked from this topic, so it is necessary that students have a good command of the topic. Try asking your teachers whatever doubts you may be having during the class and approach your friends who have solved those questions in which you are having trouble. Vedantu provides quality online resources including explanations and solved exercises which are easily accessible to the students to get a good command over the subject.