Question

Correct order of limiting molar conductivity for cations in water at 298 K is :

(1) \(H^+ > Na^+ > K^+ > Ca^{2+} > Mg^{2+}\)

(2) \(H^+ > Ca^{2+} > Mg^{2+} > K^+ > Na^+\)

(3) \(Mg^{2+} > H^+ > Ca^{2+} > K^+ > Na^+\)

(4) \(H^+ > Na^+ > Ca^{2+} > Mg^{2+} > K^+\)

Answer 1

Correct option is:  (2) \(H^+ > Ca^{2+} > Mg^{2+} > K^+ > Na^+\)  

Limiting Molar Conductivities of Ions :

• \(\overset{\oplus}{H} : 349.8\ Scm^2 \ mol^{-1}\)
• \(Na^+ : 5011 \ Scm^2 \ mol^{-1}\)
• \(K^+ :\ 73.52 \ Scm^2 \ mol^{-1}\)
• \(Ca^{+2} : 119 \ Scm^2 \ mol^{-1}\)
• \(Mg^{+2} : 106.12 \ Scm^2 \ mol^{-1}\)

Therefore correct order of limiting molar conductivity of cations will be - 

\(\overset{\oplus}{H} > Ca^{+2} > Mg^{+2} > K^+ > Na^+\)