Question

Which of the following(s) is/are true about an electrolyte solution at infinite dilution?

${\Lambda }_m$ is molar conductivity
${\Lambda }_m^0$ is limiting molar conductivity

• A. $\text{Degree of dissociation of weak electrolyte,}\alpha =1$
• B. Weak electrolyte is not fully dissociated
• C. All interionic effects of electrolyte disappears
• D. ${\Lambda }_m^0$ of an electrolyte is the sum of the individual contributions of cation and anion of the electrolyte.

Answer 1

Answer: (A), (C), (D)

${\Lambda }_m^0$ of an electrolyte is the sum of the individual contributions of cation and anion of the electrolyte.

On dilution, the molar conductivity increases.
For strong electrolyte it increases due to decreased ion- ion force of attraction.
For weak electrolyte it increase due to the increase in the degree of dissociation of the electrolyte.

At infinite dilution the weak electrolyte behaves like strong electrolyte and undergoes complete dissociation. Hence it is 100% dissociates and the degree of dissociation approaches 1.
Also, the ions are far apart and the inter ionic effects disappears.

Hence, the ion becomes totally independent of other ions. At this point, it contributes maximum towards the conductance of the solution. This value of molar conductance is known as limiting molar conductivity. It is also called as molar conductivity at infinite dilution. It is represented by ${\Lambda }_m^0$

Hence, limiting molar conductivity of an electrolyte is the sum of the individual contributions of the anion and cation of the electrolyte.

Thus, statement (a), (c) and (d) are true.