Page 1: Degree and Constant of Electrolytic Dissociation
This page introduces two fundamental concepts in electrolyte chemistry: the degree of electrolytic dissociation and the dissociation constant.
The degree of electrolytic dissociation α is explained as the ratio of dissociated molecules to the total number of molecules introduced into a solution. It can be expressed as a percentage or a fraction.
Definition: The degree of electrolytic dissociation α is the ratio of the number of moles of dissociated molecules to the number of moles of molecules introduced into the solution.
Formula: α = numberofdissociatedmolecules / totalnumberofmolecules
The document outlines factors that influence the degree of dissociation:
- Type of electrolyte
- Type of solvent
- Presence of other ions
- Electrolyte concentration lowerconcentrationleadstohigherdissociation
- Temperature highertemperatureincreasesdissociation
Highlight: The degree of dissociation ranges from 0 to 1 or0.
The page then introduces Ostwald's Dilution Law, which relates the dissociation constant to the degree of dissociation and concentration.
Formula: K = Cα² / 1−α
The dissociation constant is defined as the ratio of the product of ion concentrations formed during electrolytic dissociation to the concentration of undissociated molecules.
Definition: The dissociation constant is the ratio of the product of ion concentrations formed during electrolytic dissociation to the concentration of undissociated molecules.
Factors affecting the dissociation constant include:
- Type of electrolyte
- Solvent
- Temperature
Highlight: The dissociation constant does not depend on concentration.
The document provides an example using hydrofluoric acid HF to illustrate the dissociation process:
HF ⇌ H⁺ + F⁻
Formula: K = H+F− / HF
Finally, the page mentions a simplified formula that can be used when the degree of dissociation α is less than 5%:
Formula: K = Cα² whenα<5
This simplified version of Ostwald's Dilution Law is applicable in cases of weak electrolytes or very dilute solutions.
