CHEMISTRY SLET QUESTION
The increase in conductance of an electrolyte at very high potential gradients (approx. 105 V/cm) is known as:
- (A) Walden effect
- (B) Wien effect
- (C) Debye-Falkenhagen effect
- (D) Electrophoretic effect
Correct Answer: (B) Wien effect
The Wien effect refers to the phenomenon where the electrical conductivity of an electrolyte increases when a very high electric field (potential gradient) is applied.
Why it happens: Under a very high potential gradient, ions move with such high velocity that they "escape" their ionic atmosphere before it has time to reform. This effectively eliminates both the asymmetry effect and the electrophoretic effect, leading to a significant rise in molar conductance toward its limiting value.
Comparison: Unlike the Debye-Falkenhagen effect (which relies on high frequency), the Wien effect relies on high field strength.