Factors Affecting Electrolytic Conductance

The conductance of an electrolytic solution is not a fixed number for a given electrolyte — it depends on several physical factors that either help or hinder how freely the dissociated ions can move through the solution. This section collects the main ones:

• Interionic attraction. The stronger the electrostatic attraction between the oppositely-charged ions of the solute, the more that attraction drags against their independent motion, so conductance decreases as interionic attraction increases. This effect is strongest at high concentration, where ions are packed closely together.
• Dielectric constant of the solvent. A solvent with a higher dielectric constant is more effective at screening the charges on dissolved ions from each other, weakening interionic attraction and so promoting greater dissociation and higher conductance. This is part of why water — with its unusually high dielectric constant — is such an effective solvent for ionic compounds.
• Viscosity of the medium. Conductance is inversely proportional to viscosity: a more viscous medium physically resists the movement of ions through it (a larger 'viscous drag'), so conductivity rises as viscosity falls.
• Temperature. Raising the temperature of an electrolytic solution increases conductance, because the added kinetic energy lets ions move faster and also weakens the attractive forces holding oppositely-charged ions close together, both of which favour freer ionic motion. …