A Clear Explanation on The Key Concept of Ionic Equilibrium

Have you ever observed what happens when raisins are submerged in water for a few hours? The raisins swell, and the liquid becomes brown. What exactly is going on inside? Water gets into the raisins via their skin, and some of the raisin juice seeps out into the water, turning the water brown. Between the raisin juice and the water, a balance is reached at some point.

Other examples of achieving this kind of an equilibrium can be seen in everyday life. Carbonated water in a soda bottle, for example, contains a balanced ratio of carbonic acid to carbon dioxide (the bubbles) and water.In addition, when the concentration of common salt rises, so does the conductivity of electricity.

Definition And Calculation of Ionic Equilibrium

Ionic equilibrium can be defined as the equilibrium between unionised molecules and ions in the solution of weak electrolytes. For example, acetic acid which breaks down into acetate ions and hydrogen ions:

CH₃COOH → CH₃COO^– + H⁺

Electrolytes are those chemical substances that can conduct electricity in their aqueous or molten states. At a specific temperature, the product of hydroxyl ion and hydrogen ion concentrations in pure water or an aqueous solution is a constant. This is called the ionic product of water, and  can usually be denoted by K_w.

The concept of the ionic product of water can be explained by considering the autoionization reaction of water, which can be written as:

H₂ O + H₂ O = H₃ O⁺ + OH^–

K_w = C_H3O⁺ C_OH^–

K_w at 25°C is 1*10^-14.

The hydrogen ion concentration of a solution is of primary importance in the study of acid-base equilibria in aqueous solutions. The hydrogen ion concentrations in the solutions we work with are typically negative powers of 10.

The concentration of hydrogen ions within a solution is measured by pH. It’s a measurement of a solution’s acidity or alkalinity. Acidic aqueous solutions with a pH less than seven at 25°C are acidic, while basic or alkaline aqueous solutions with a pH more than seven are basic or alkaline.

The following formula can be used to calculate pH.

pH = -log C_H3O⁺

Concept of Ionic Equilibrium

Many electrolytes are almost fully transformed to ions when dissolved in water. Strong electrolytes are electrolytes that have a high concentration of ions. Strong electrolytes include  NaCl, KCl, KNO₃, NH₄Cl.   A single arrow is used to illustrate the process of ion formation (ionisation or dissociation) in their case.

NaCl(aq) → Na⁺(aq)+ Cl^– (aq)

HCl(g)+ H₂O(l) →  H₃O⁺(aq)+ Cl^– (aq)

Many electrolytes, on the other hand, only partially ionises. Weak electrolytes are electrolytes that aren’t as strong as strong electrolytes. Many covalent compounds are weak electrolytes, such as CH₃COOH, NH₄OH, and C₆H₅NH₃. Such a chemical exists partially in the unionised molecular form and partly in the form of ions in its solution.

When the rates of ionisation of molecules to form ions and the rate of combining of ions to form molecules equalise, a dynamic equilibrium is achieved between the two forms. Ionic equilibrium is a type of equilibrium that involves ions. Reversible arrows are used to show the equilibrium between unionised molecules and ions. Consider the following scenario:

CH₃COOH(l) +H₂O(l) → H₃O⁺ (aq)+ CH₃COO^– (aq)

The degree of ionisation is used to represent the extent to which a weak electrolyte ionises. The fraction or percentage of the total amount (or concentration) of the electrolyte that is present in the form of ions is known as degree of ionisation.

Types of Ionic Equilibrium

Michael Faraday divided the chemicals into two categories depending on their capacity to conduct electricity-

1. Non- electrolytes- Substances which do not conduct electricity are known to be nonelectrolytes. Non-polar covalent compounds belong to the class. Sugar, benzene, glucose are the examples.
2. Electrolytes- Electrolytes are chemical substances that may conduct electricity in their aqueous or molten states. Ionic compounds belong to the class. They conduct electricity due to ion formation by dissociation of substances. 

Strong and weak electrolytes are two categories of electrolytes in ionic equilibrium.

Strong electrolytes are chemicals that ionise entirely when dissociated in their ionic solution, whereas weak electrolytes only dissociate partially.

• The dissociation reaction can be considered to be complete with respect to strong electrolyte, going solely in one direction, but the reaction is considered to be reversible in nature in the case of a weak electrolyte.
• The equilibrium between the ions and the unionised molecules is established in the case of a weak electrolyte, which is known as ionic equilibrium. 

Conclusion

With the completion of the whole article, we have come to know about the ionic equilibrium and its types. Ionic equilibrium helps us understand the chemical reaction and the strength of the acid and bases.