Theory of Strong Electrolytes

The theory of strong electrolytes describes these substances as ionizing completely in solution at all concentrations up to their saturation point. Despite complete ionization, molar conductance decreases with increasing concentration due to stronger interionic attractions that hinder ionic mobilities rather than incomplete dissociation.

The dielectric constant measures a solvent's ability to store electrical energy based on its polarizability. In high-dielectric solvents like water, electrostatic forces between ions are relatively weak. In low-dielectric solvents or concentrated solutions, stronger interionic forces may cause ions to pair up as ionic doublets despite being fully ionized.

Each ion is surrounded by an ionic atmosphere of oppositely charged ions, shaped by coulombic interactions and thermal collisions between ions and solvent molecules. At high temperatures, this structure becomes less organized due to increased thermal collisions, affecting the overall electrostatic environment around each ion.

When an electric field is applied, ions move and disrupt the ionic atmosphere's symmetry. This asymmetry effect slows down the central ion's movement because the surrounding ionic atmosphere no longer shields it uniformly, increasing resistance to motion through the solution.

The electrophoretic effect occurs when the ionic atmosphere and related solvent molecules move in the opposite direction of the central ion, creating counter-currents that impede ion movement. This opposing flow further reduces ionic mobility and conductance beyond the asymmetry effect alone.

The viscous effect results from the solvent's viscous drag on ion movement. The more viscous the solvent, the stronger the frictional drag on ions, resulting in decreased ionic mobility and conductance. This effect combines with asymmetry and electrophoretic effects to reduce overall electrical conductance.

Debye and Hückel introduced the concept that molar conductance increases with dilution because of heightened ion mobilities from reduced interionic attractions, not increased ionization. The Debye–Huckel–Onsager Conductance Equation measures the impact of interionic effects on conductivity in strong electrolyte solutions.