Question

Define Specific Conductivity and Cell Constant, including their units.

Hint:

Cell constant remains fixed for a given conductivity cell, while specific conductivity changes with concentration and temperature.

Answer 1

Concept: Conductance of electrolytic solutions depends on both the nature of the solution and the geometry of the conductivity cell. Specific conductivity and cell constant help standardize these measurements.
1. Specific Conductivity (Conductivity, \( \kappa \)): Definition: Specific conductivity is the conductance of a solution contained between two electrodes that are 1 cm apart and have a cross-sectional area of \(1\,\text{cm}^2\). It measures the ability of ions to conduct electricity in a solution. Formula: \[ \kappa = \frac{1}{R} \cdot \frac{l}{A} \] where,
\( R \) = resistance
\( l \) = distance between electrodes
\( A \) = cross-sectional area
Unit: \[ \text{S cm}^{-1} \quad \text{(or SI unit: S m}^{-1}) \]
2. Cell Constant: Definition: Cell constant is the ratio of the distance between the electrodes to the cross-sectional area of the electrodes. \[ \text{Cell constant} = \frac{l}{A} \] It depends only on the geometry of the conductivity cell. Unit: \[ \text{cm}^{-1} \]
Relation Between Them: \[ \kappa = \text{Conductance} \times \text{Cell constant} \]