Degree of Dissociation

What is this formula?

The degree of dissociation represents the fraction of a substance that dissociates into ions or smaller species at equilibrium.

When to use it

Use this formula when studying weak acids, weak bases, electrolytes, and chemical equilibrium systems where only part of the original substance dissociates.

Example

Given:

Initial amount of acetic acid = 0.100 mol

Amount dissociated = 0.0042 mol

Formula:

α = nd / n0

Substitution:

α = 0.0042 / 0.100

Result:

α = 0.042

The acid is 4.2% dissociated.

Applications

Weak acid analysis

Weak base analysis

Electrolyte chemistry

Equilibrium calculations

Physical chemistry

Chemical education

Note

The degree of dissociation is a dimensionless quantity ranging from 0 to 1. In practice, it depends on concentration, temperature, ionic strength, and the nature of the solute. Strong electrolytes typically have values close to 1, while weak acids and weak bases often have much smaller values.

Some textbooks express the result as a percentage by multiplying α by 100. In fCalc, the primary result is stored as a fraction to maintain consistency with equilibrium calculations.