Degree of Dissociation
The fraction of the original substance that has broken apart at equilibrium.
Formula / equation
α = amount dissociated / initial amount
Unit
Dimensionless
In depth
Ranging from zero to one, the degree of dissociation can be determined from measurements of vapour density, conductivity or colligative properties. It increases with dilution for reactions producing more particles, a result formalised in Ostwald's dilution law.
Examples in the real world
PCl₅ is about 80% dissociated at 250 °C and 1 atm; dilute ethanoic acid is only about 1.3% dissociated.