The Electrolytic dissociation theory Refers to the separation of the molecule from an electrolyte into its constituent atoms.
Electron dissociation is the separation of a compound in its ions into the incoming solution. Electrolytic dissociation occurs as a result of the interaction of solute and solvent.
Results from spectroscopes indicate that this interaction is mainly chemical in nature.
In addition to the solubility of the solvent molecules and the solvent's dielectric constant, a macroscopic property also plays an important role in electrolytic dissociation.
The classical theory of electrolytic dissociation was developed by S. Arrhenius and W. Ostwald during the 1880s.
It is based on the presumption of incomplete dissociation of the solute, characterized by the degree of dissociation, which is the fraction of the dissociated electrolyte molecules.
The dynamic equilibrium between dissociated molecules and ions is described by the law of mass action.
There are several experimental observations that support this theory, including: the ions present in the solid electrolytes, the application of the Ohm's Law, the ionic reaction, the neutralization heat, the colligative abnormal properties, and the color of the solution between others.
Theory of electrolytic dissociation
This theory describes aqueous solutions in terms of acids, which are dissociated to provide hydrogen ions, and bases, which dissociate to provide hydroxyl ions. The product of an acid and a base is salt and water.
This theory was exposed in 1884 to explain the properties of electrolytic solutions. It is also known as ionic theory.
Main principles of theory
When an electrolyte is dissolved in water, it is separated into two types of charged particles: one charging a positive charge and the other with a negative charge.
These charged particles are called ions. Positively charged ions are called cations and those which are negatively charged are referred to as anions.
In its modern form, the theory assumes that solid electrolytes are composed of ions that are held together by the electrostatic forces of attraction.
When an electrolyte is dissolved in a solvent, these forces are weakened and then the electrolyte undergoes a dissociation in ions; The ions are dissolved.
The process of separating molecules into ions from an electrolyte is called ionization. The fraction of the total number of molecules present in the solution as ions is known as the degree of ionization or degree of dissociation. This degree can be represented by the symbol α.
It has been observed that all electrolytes do not ionize at the same level. Some are almost completely ionized, while others are weakly ionized. The degree of ionization depends on several factors.
The ions present in the solution are constantly re-joined to form neutral molecules, thus creating a state of dynamic equilibrium between ionized and non-ionized molecules.
When an electric current is transmitted through the electrolytic solution, the positive ions (cations) move towards the cathode, and the negative ions (anions) move towards the anode to be discharged. This means that electrolysis occurs.
Electrolytic Solutions
Electrolytic solutions are always neutral in nature since the total charge of one set of ions is always equal to the total charge of the other set of ions.
However, it is not necessary that the number of the two sets of ions should always be equal.
The properties of the electrolytes in the solution are the properties of the ions present in the solution.
For example, an acidic solution always contains H + ions while the basic solution contains OH- ions and the characteristic properties of the solutions are those with H- and OH- ions, respectively.
Ions act as molecules toward freezing point depression, raising the boiling point, lowering vapor pressure and establishing osmotic pressure.
The conductivity of the electrolytic solution depends on the nature and number of ions when the current is charged through the solution by the movement of ions.
The ions
The classical theory of electrolytic dissociation is applicable only to dilute solutions of weak electrolytes.
Strong electrolytes in the diluted solutions are virtually completely dissociated; Consequently the idea of a balance between ions and dissociated molecules is not important.
According to the chemical concepts, the pairs of ions and the most complex aggregates are formed in solutions of strong electrolytes in medium and high concentrations.
Modern data indicate that ion pairs consist of two oppositely charged ions in contact or separated by one or more solvent molecules. Ion pairs are electrically neutral and do not participate in the transmission of electricity.
In relatively dilute solutions of strong electrolytes, the balance between individually dissolved ions and ion pairs may be described in approximately a manner similar to the classical theory of electrolytic dissociation by constant dissociation.
Factors related to the degree of ionization
The degree of ionization of an electrolytic solution depends on the following factors:
- Nature of the solute : When the ionizable parts of the molecule of a substance are joined by covalent bonds rather than electrovalent bonds, fewer ions are supplied in the solution. These substances are determined weak electrolytes. On the other hand, strong electrolytes are almost completely ionized in the solution.
- Nature of solvent : The main function of the solvent is to weaken the electrostatic forces of attraction between two ions to separate them. Water is considered the best solvent.
- Dilution : The ionization capacity of an electrolyte is inversely proportional to the concentration of its solution. Therefore, the degree of ionization increases with increasing dilution of the solution.
- Temperature : The degree of ionization increases with increasing temperature. This is because at higher temperatures, the molecular rate increases, surpassing the attraction forces between the ions.
References
- Electrolytic dissociation. Retrieved from dictionary.com.
- Electrolytic dissociation. Retrieved from encyclopedia2.thefreedictionary.com.
- Theory of Electrolytic Dissociation. Retrieved from vocabulary.com.
- Arrhenius theory of electrolytic dissociation. Retrieved from askiitians.com.