Q. The ionic conductances of following cations in a given concentration are in the order
A) $Li^{+} < Na^{+} < K^{+} < Rb^{+}$
B) $Li^{+} > Na^{+} > K^{+} > Rb^{+}$
C) $Li^{+} < Na^{+} > K^{+} > Rb^{+}$
D) $Li^{+} = Na^{+} < K^{+} < Rb^{+}$
Explanation
(a)
Conductance of an ion is dependent upon its size – as follows :
$Ionic\ conductance\ \propto \frac{1}{ionic\ \ size}$
Thus, ionic conductance in aqueous solution increases in the order-
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ Cs^{+} < Rb^{+} < K^{+} < Na^{+} < Li^{+}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.