Equivalent Conductance vs. Molar Conductance

Attribute	Equivalent Conductance	Molar Conductance
Definition	Measure of the conductivity of an electrolyte solution containing one equivalent of the electrolyte	Measure of the conductivity of an electrolyte solution containing one mole of the electrolyte
Symbol	Λeq	Λm
Units	S m² mol⁻¹ eq⁻¹	S m² mol⁻¹
Dependence on Concentration	Depends on the concentration of the electrolyte	Depends on the concentration of the electrolyte
Dependence on Temperature	Depends on the temperature of the solution	Depends on the temperature of the solution
Calculation	Λeq = κ / c	Λm = κ / c
Summation Rule	Λeq = Λ₁ + Λ₂ + ... + Λn	Λm = Λ₁ + Λ₂ + ... + Λn
Relation to Conductivity	κ = Λeq * c	κ = Λm * c

Introduction

When studying the behavior of electrolytes in solution, two important concepts come into play: equivalent conductance and molar conductance. These terms are often used interchangeably, but they have distinct attributes that are worth exploring. In this article, we will delve into the differences and similarities between equivalent conductance and molar conductance, shedding light on their significance in the field of chemistry.

Definition and Calculation

Equivalent conductance (Λ_eq) is a measure of the conductivity of an electrolyte solution containing one equivalent of the electrolyte. An equivalent is the amount of an electrolyte that carries one mole of electrical charge. On the other hand, molar conductance (Λ_m) is the conductivity of a solution containing one mole of the electrolyte. It is calculated by dividing the equivalent conductance by the concentration of the electrolyte in moles per liter (M).

Units of Measurement

Equivalent conductance is typically expressed in units of siemens per centimeter per equivalent (S·cm²·eq^-1), while molar conductance is expressed in siemens per centimeter per mole (S·cm²·mol^-1). These units reflect the relationship between the amount of charge carried by the electrolyte and the distance it travels through the solution.

Dependence on Concentration

One key distinction between equivalent conductance and molar conductance lies in their dependence on concentration. Equivalent conductance is independent of concentration, meaning it remains constant regardless of the concentration of the electrolyte. This is because equivalent conductance is a measure of the conductivity of a solution containing one equivalent of the electrolyte, which is a fixed amount of charge. On the other hand, molar conductance is dependent on concentration. As the concentration of the electrolyte increases, the molar conductance decreases due to the increased number of ions experiencing interionic interactions and collisions.

Temperature Dependence

Both equivalent conductance and molar conductance are influenced by temperature. As the temperature increases, the conductance of an electrolyte solution generally increases. This is due to the increased mobility of ions at higher temperatures. However, the effect of temperature on equivalent conductance and molar conductance differs. Equivalent conductance typically increases more rapidly with temperature compared to molar conductance. This is because the increase in temperature not only enhances the mobility of ions but also reduces the viscosity of the solution, allowing for easier ion movement.

Electrolyte Strength

Equivalent conductance and molar conductance provide valuable insights into the strength of an electrolyte. Strong electrolytes, which dissociate completely into ions in solution, exhibit higher equivalent conductance and molar conductance values compared to weak electrolytes. This is because strong electrolytes produce a greater number of ions, leading to higher conductivity. By comparing the conductance values of different electrolytes, it is possible to determine their relative strengths and their ability to conduct electricity.

Ion Size and Conductance

The size of ions in an electrolyte solution also affects both equivalent conductance and molar conductance. Smaller ions tend to have higher conductance values compared to larger ions. This is because smaller ions experience less resistance as they move through the solution, resulting in higher mobility and conductivity. Therefore, electrolytes composed of smaller ions generally exhibit higher conductance values than those composed of larger ions.

Limitations and Practical Applications

While equivalent conductance and molar conductance provide valuable information about the behavior of electrolytes, they have certain limitations. Both conductance values are typically measured at infinite dilution, which means they may not accurately represent the behavior of electrolytes at higher concentrations. Additionally, the presence of other ions or solutes in the solution can affect the conductance values. Despite these limitations, equivalent conductance and molar conductance are widely used in various fields, including electrochemistry, chemical analysis, and industrial processes.

Conclusion

Equivalent conductance and molar conductance are important concepts in the study of electrolytes. While equivalent conductance represents the conductivity of a solution containing one equivalent of an electrolyte, molar conductance measures the conductivity of a solution containing one mole of the electrolyte. They differ in their dependence on concentration, units of measurement, and temperature dependence. However, both provide valuable insights into the strength of electrolytes and the behavior of ions in solution. By understanding the attributes of equivalent conductance and molar conductance, chemists can better analyze and predict the behavior of electrolytes in various applications.