Question

${\wedge }_m={\wedge }_m^o-k\sqrt{C}$ is valid for

• A. Weak electrolytes only
• B. strong electrolytes only
• C. both weak and strong electrolytes

Answer 1

The correct option is B strong electrolytes only

For strong electrolytes, such as salts, strong acids and strong bases, the molar conductivity depends only weakly on concentration. Based on experimental data Friedrich Kohlrausch (around the year 1900) proposed the non-linear law for strong electrolytes:
${\wedge }_m={\wedge }_m^o-k\sqrt{C}$
where ${\wedge }_m^o$ is the molar conductivity at infinite dilution (or limiting molar conductivity) K is the Kohlrausch coefficient, which depends mainly on the stoichiometry of the specific salt in solution.
This law is valid for low electrolyte concentrations only; it fits into the Debye-Hückel-Onsager equation. For weak electrolytes (i.e. incompletely dissociated electrolytes), however, the molar conductivity strongly depends on concentration: The more dilute a solution, the greater its molar conductivity, due to increased ionic dissociation.