Question

The variation of molar conductivity for a uni-univalent electrolyte versus the electrolyte concentration is given by $A_M=a+b\sqrt{c}$. Point out the correct facts about this empirical equation:

• A. it was derived by Kohlrausch from experimental data
• B. the empirical equation is valid only for strong electrolytes
• C. the intercept of $A_{M}vs.\sqrt{c}$ curve leads to limiting molar conductivity of strong electrolyte at infinite dilution
• D. $A_M^{\infty }={\lambda }_{cation}^{\infty }+{\lambda }_{anion}^{\infty }$

Answer 1

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

The correct options are
A $A_M^{\infty }={\lambda }_{cation}^{\infty }+{\lambda }_{anion}^{\infty }$
B the intercept of $A_{M}vs.\sqrt{c}$ curve leads to limiting molar conductivity of strong electrolyte at infinite dilution
C it was derived by Kohlrausch from experimental data
D the empirical equation is valid only for strong electrolytes

By experimental observations, Kohlrausch derived the empirical equation $A_m=a+b\sqrt{c}$.

This equation is applicable for strong electrolytes and does not holds good for weak electrolytes.

The intercept of the plot of $A_{M}vs.\sqrt{c}$ curve gives limiting molar conductivity of strong electrolyte at infinite dilution.

The limiting molar conductivity has contributions from the cations and the anions.

$A_M^{\infty }={\lambda }_{cation}^{\infty }+{\lambda }_{anion}^{\infty }$

Thus, all the four options are correct.