Arrhenius Theory of Ionization

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Arrhenius Theory of Ionization

Published by: Nuru

Published date: 26 Jun 2021

Arrhenius Theory of Ionization in Grade 12

Arrhenius Theory of Ionization

Arrhenius Theory of Ionization Concept:

Arrhenius theory introduced in 1887 by the Swedish scientist Svante Arrhenius. It states that acids are substances that dissociate in water to yield electrically charged atoms or molecules, called ions, one of which is a hydrogen ion (H+), and that bases ionize in water to yield hydroxide ions (OH−). Some examples include: When sodium and chlorine combine to make salt, the sodium atom gives up an electron resulting in a positive charge while chlorine gets the electron and becomes negatively charged as a result.

Some fundamental postulates of Arrhenius theory of ionization-

  • When any electrolyte is dissolved in water, it splits up into electrically charged particles called ions. This process is known as ionization or dissociation. Positively charged particle is called cations while negatively charged particles are called anions.
  • The total number of cations is always equal to the number of anions in a solution. So, the solution as a whole is electrically neutral.
  • The electrical conductivity of the electrolyte in a solution is due to the migration of anions towards oppositely charged electrodes.
  • The process of ionization is reversible. Ions are reuniting to give undissociated molecules and at the same time, undissociated molecules are ionizing. So, a dynamic equilibrium is established between ions and the dissociated molecules.
  • The process of ionization is not completed. The extent of ionization is expressed in the degree of ionization which is denoted by α. Thus the degree of ionization is defined as the fraction of the total number of moles of electrolyte which split into ions.

Degree of Ionization ( α) = no. of moles of electrolytes which split into ion / total no. of moles of electrolytes dissolved

The electrical conductivity of the electrolyte in the solution is the number of ions produced by them.

degree of ionization