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

‘B’ is strong electrolyte because on dilution of a strong electrolyte, number of ions almost remains the same. Only interionic attraction decreases and therefore increase in limiting molar conductivity of ‘B’ is small. Or we can say that,

⇒ On dilution for both strong and weak electrolyte, there is increase in molar conductivity.

⇒ But, it has been observed that there is a large increase in molar conductivity of weak electrolyte on dilution than strong electrolyte. Because, weak electrolyte dissociates very less at higher concentration.

⇒ On dilution, degree of dissociation of weak electrolyte increases means there is increase in number of ions per unit volume.

⇒ On the other hand, for strong electrolyte, degree of dissociation increases slowly on dilution.

⇒ Thus, ‘B’ whose limiting molar conductivity of ‘B’ increases 1.5 times is strong electrolyte.