Question

The molar conductance of $NaCl , HCl$ and $CH _{3} COONa$ at infinite dilution are $126.45,426.16$ and $91.0 \,S \,cm ^{2} \,mol ^{-1}$ respectively. The molar conductance of $CH _{3} COOH$ at infinite dilution is. Choose the right option for your answer.

• A. $201.28 \,S \,cm ^{2} mol ^{-1}$
• B. $390.71\, S\, cm ^{2} mol ^{-1}$
• C. $698.28 \,S \,cm ^{2} mol ^{-1}$
• D. $540.48\, S\, cm ^{2} mol ^{-1}$

Answer 1

Answer: (B)

$\lambda_{ M }^{ CH _{3} COOH }=\lambda_{ CH _{3} COO^- }^{ M }+\lambda_{ Na ^{+}}^{ M }+\lambda_{ H ^{+}}^{ M }+\lambda_{ Cl^- }^{ M }-\lambda_{ Na ^{+}}^{ M }-\lambda_{Cl^-}^{ M }$
$=\lambda_{ CH _{3} COONa }^{ M }+\lambda_{ HCl }^{ M }-\lambda_{ NaCl }^{ M }$
$=91+426.16-126.45$
$=390.71 \,S\,cm ^{2} mole ^{-1}$