Read the passage carefully and answer the questions.

The resistance (R) of an object is given by the expression $ρ\frac{l}{A}$. The inverse of R is called conductance and the inverse of $ρ$ is called conductivity or specific conductance represented by K. The conductivity depends upon the nature of the material (insulator, semiconductor or conductor) and the temperature of the substance. Similarly, the conductance due to the ions present in the solution (ionic conductance) depends upon the nature of the electrolyte, size of the ions produced, the nature of the solvent and the temperature. Molar conductivity ($Λ_m$) of a solution at a given concentration is the conductance of the volume V of solution containing one mole of electrolyte kept between two electrodes with area of cross-section A and the distance of unit length. It is given by the expression, $Λ_m = kV$. Molar conductivity increases with the decrease in concentration and when the concentration approaches zero, it is called limiting molar conductivity. The decrease is linear in the case of a strong electrolyte. However, in the case of a weak electrolyte, the change in molar conductivity is gradual in the higher concentration range and there is a sharp increase in molar conductivity as the concentration approaches zero. From the limiting molar conductivity values of a strong electrolyte, we can find the limiting molar conductivity of a weak electrolyte containing the common ions using the Kohlrausch law of independent migration of ions. From molar conductivity and limiting molar conductivity, we can Am determine the degree of dissociation ($\frac{Λ_m}{Λ_m^o}$) and ionization constant of a weak acid.

Select the correct statement.

Molar conductivity increases with the decrease in concentration for both strong and weak electrolytes.

The correct answer is Option (1) → Molar conductivity increases with the decrease in concentration for both strong and weak electrolytes.

Molar conductivity (Λₘ) is defined as the conductance of all the ions produced by one mole of an electrolyte in solution.

Formula:

Λₘ = κ / C

where

κ = conductivity

C = concentration

Effect of dilution

When the concentration decreases (dilution increases):

• The distance between ions increases, reducing interionic attraction.
• Ionic mobility increases.
• In weak electrolytes, degree of ionization also increases.

Thus molar conductivity increases with dilution.

Strong electrolytes

Strong electrolytes are almost completely ionized in solution.

When diluted:

• Interionic attractions decrease.
• Ionic mobility increases slightly.

Therefore molar conductivity increases gradually with dilution.

Weak electrolytes

Weak electrolytes are partially ionized.

When diluted:

• Degree of ionization increases significantly.
• More ions are produced.

Thus molar conductivity increases sharply with dilution.

Option-wise Explanation

Option 1: Molar conductivity increases with the decrease in concentration for both strong and weak electrolytes

Dilution increases ionic mobility and ionization (for weak electrolytes), causing molar conductivity to increase. Hence this option is correct.

Option 2: Molar conductivity decreases with the decrease in concentration for both strong and weak electrolytes

This is opposite to the actual behavior observed during dilution. Hence this option is incorrect.

Option 3: Molar conductivity decreases with the decrease in concentration for strong electrolytes only

Strong electrolytes also show an increase in molar conductivity upon dilution. Therefore this option is incorrect.

Option 4: Molar conductivity decreases with the decrease in concentration for weak electrolytes only

Weak electrolytes actually show a large increase in molar conductivity upon dilution. Hence this option is incorrect.