Q. 41

# Solutions of two electrolytes ‘A’ and ‘B’are diluted. The of ‘B’ increases 1.5 times while that of A increases 25 times. Which of the two is a strong electrolyte? Justify your answer.

Answer :

Molar conductivity of a solution at a given concentration is the conductance of volume V of a solution containing one mole of electrolyte kept between two electrodes with an area of cross section A and distance of unit length.

Molar conductivity, Λ_{m}= or Λ_{m=} κV

where

κ is the conductivity

A is the area of cross-section and

l is the distance between the electrodes.

For weak electrolytes the number of ions increases and the degree of dissociation increases with dilution and the increase is drastic. Hence, A has to be a weak electrolyte whereas B has to be a strong electrolyte because for strong electrolytes the number of ions does not change, but interionic distance decreases and therefore the increase is gradual.

Thus, electrolyte B is strong as on dilution the number of ions remains the same, only interionic attraction decreases; therefore, the increase in Λ_{m} is small.

Rate this question :

Match the items of Column I and Column II.

Assertion : Conductivity of all electrolytes decreases on dilution.

Reason : On dilution number of ions per unit volume decreases.

Chemistry - Exemplar