Question

The ionic conductance of following cations in a given conc. is in the order

• A. $Li^+ < Na^+ < K^+ < Rb^+$
• B. $Li^+ > Na^+ > K^+ > Rb^+$
• C. $Li^+ < Na^+ > K^+ > Rb^+$
• D. $Li^+ = Na^+ < K^+ < Rb^+$

Answer 1

Answer: (A)

$Li^+ < Na^+ < K^+ < Rb^+$

Answer 2

Due to extensive hydration of smaller alkali metal cations, the ionic radii is in the order $Li^+ > Na^+ > K^+ > Rb^+$ As such mobility in water is in the order $Li^+ < Na^+ < K^+ < Rb^+$