Explain with the help of a diagram the effect of change in concentration of solution on molar conductivity of : (i) a weak electrolyte, (ii) a strong electrolyte.

To understand how the concentration of a solution affects its molar conductivity, we need to differentiate between weak and strong electrolytes. Molar conductivity is a measure of how well an electrolyte conducts electricity in solution, and it varies with concentration due to the nature of the electrolyte. Let’s break this down for both types of electrolytes and illustrate the concepts with diagrams.

Understanding Molar Conductivity

Molar conductivity (\( \Lambda_m \)) is defined as the conductivity (\( \kappa \)) of a solution divided by its molar concentration (\( C \)). Mathematically, it can be expressed as:

\( \Lambda_m = \frac{\kappa}{C} \)

Weak Electrolytes

Weak electrolytes, such as acetic acid (CH₃COOH), only partially dissociate into ions in solution. As the concentration of a weak electrolyte increases, the degree of dissociation decreases due to the common ion effect and increased ion pairing. This leads to a decrease in molar conductivity with increasing concentration.

Diagram for Weak Electrolyte

Imagine a graph where the x-axis represents the concentration of the weak electrolyte and the y-axis represents molar conductivity. The curve would start high at low concentrations and gradually decline as concentration increases, indicating that molar conductivity decreases.

Strong Electrolytes

In contrast, strong electrolytes like sodium chloride (NaCl) completely dissociate into ions in solution. As the concentration of a strong electrolyte increases, the number of ions in solution increases, leading to higher conductivity. However, at very high concentrations, the conductivity may level off or even decrease slightly due to ion interactions and limited mobility.

Diagram for Strong Electrolyte

For strong electrolytes, the graph would show a linear increase in molar conductivity with concentration at lower concentrations, eventually reaching a plateau or a slight decrease at very high concentrations.

Key Takeaways

• Weak Electrolytes: Molar conductivity decreases with increasing concentration due to decreased dissociation.
• Strong Electrolytes: Molar conductivity generally increases with concentration, but may plateau at high concentrations due to ion interactions.

In summary, the behavior of molar conductivity in relation to concentration varies significantly between weak and strong electrolytes. Understanding these differences is crucial for applications in chemistry, such as in electrochemistry and solution chemistry.