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 = (number of dissociated molecules) / (total number of molecules)
The document outlines factors that influence the degree of dissociation:
- Type of electrolyte
- Type of solvent
- Presence of other ions
- Electrolyte concentration (lower concentration leads to higher dissociation)
- Temperature (higher temperature increases dissociation)
Highlight: The degree of dissociation ranges from 0 to 1 (or 0% to 100%).
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 (when α < 5%)
This simplified version of Ostwald's Dilution Law is applicable in cases of weak electrolytes or very dilute solutions.
