Q. If the molar conductance value of ${Ca}^{2 +}$ and ${Cl}^{-}$ at infinite dilution are respectively $118.88 \times 10^{- 4}\ m^{2}\ mho\ mol^{- 1}\$ and 77.33 $\times 10^{- 4}\ m^{2}\ mho\ mol^{- 1}\$ then that of $CaCl_{2}$ is (in $m^{2}\ mho\ mol^{- 1}\$ )

A) 118.88 $\times 10^{- 4}$
B) 154.66 $\times 10^{- 4}$
C) 273.54 $\times 10^{- 4}$
D) 196.21 $\times 10^{- 4}$
Explanation

(c)
From Kohlrausch’s law
$\Lambda_{m}^{\infty} = \ v_{+}\ \lambda_{+}^{\infty} + \ v_{-}\ \lambda_{-}^{\infty}$
For ${CaCl}_{2}$
$\Lambda_{m}^{\infty}({CaCl}_{2})\ \ = \ \Lambda_{Ca^{2 +}}^{\infty} + \ {2\Lambda}_{{Cl}^{-}}^{\infty}$
$= \ 118.88\ \times \ 10^{- 4\ } + \ 2\ \times \ 77.33\ \times \ 10^{- 4}$
$= \ 118.88\ \times \ 10^{- 4}\ \ + \ 154.66\ \times \ 10^{- 4}$
$= \ 273.54\ \times 10^{- 4}\ \ m^{2}\ mho\ {mol}^{- 1}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.