Conductance

Concept: Molar conductivity ( ) is defined as the conducting power of all the ions produced by one mole of an electrolyte in solution. It is related to conductivity and concentration by the relation: where

• = Molar conductivity
• = Conductivity of the solution
• = Concentration of electrolyte

On dilution, the distance between ions increases and interionic attraction decreases, allowing ions to move more freely.
Step 1: {Observe the mathematical relation.} From this relation, molar conductivity is inversely proportional to concentration.
Step 2: {Effect of decreasing concentration.} When concentration decreases: Therefore, molar conductivity increases.
Step 3: {Physical explanation.} On dilution:

• Interionic attraction decreases
• Ionic mobility increases
• Degree of ionization increases (especially for weak electrolytes)

Thus, molar conductivity increases with dilution. Hence, the correct option is (B) Increase.

Concept: Molar conductivity ( ) is defined as the conductivity of the solution containing one mole of electrolyte. It is related to conductivity and concentration by the relation: where

• = Molar conductivity
• = Conductivity of solution
• = Concentration of electrolyte in

The factor 1000 is used to convert litres to since .
Step 1: {Write the definition of molar conductivity.} where is the volume containing one mole of electrolyte.
Step 2: {Express volume in terms of concentration.} If the concentration of solution is mol L , Converting litres into :
Step 3: {Substitute the value of volume in the equation.} Thus, the correct relation is option (C).