Arrhenius Theory of Ionization Definition Postulates & Concept

The Arrhenius theory of ionization, which is named after the Swedish scientist 7th August Arrhenius, explains why some substances are soluble in water while others are not. The theory states that when a gas dissolves in water it breaks down into its component ions. These ions will either be positively or negatively charged and this charge can make them more or less likely to bond with other particles around them.

This post talks about what causes the difference between those substances that dissolve easily and those that don’t as well as how pH level affects solubility levels.

Postulates of Arrhenius’s Theory of Ionization

The main postulates of Arrhenius’s Theory of Ionization are:

  1. Electrolytes contain electrically charged particles called ions.
  2. Electrolytes dissociate into the oppositely charged ions in water.
  3. The number of positive and negative charges on the ions must be equal.
  4. Ionization is a reversible process in the solution containing ionized and un-ionized electrolyte molecules.
  5. The degree of ionization depends upon the nature of the electrolyte. Strong electrolytes (NaCl) ionize completely while weak electrolytes (CH3COOH) ionize incompletely.
  6. On passing the electric current, the cation moves towards the cathode while anions move towards the anode.
  7. Dissociation of the electrolytes depends upon (i) the nature of the electrolyte (ii) the Degree of dilution (iii) Temperature.
  8. Electrical conductivity depends upon the (i) Number of Ions present in the solution (ii) Speed of ions.

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