Question

The ionic conductance of $Ba^{2+}$ and $Cl^{-}$ respectively are $127$ and $76\, \Omega^{-1} cm^2$ at infinite dilution. The equivalent conductance of $BaCl_2$ at infinite dilution will be

• A. $330\, \Omega^{-1} cm^2$
• B. $203\, \Omega^{-1} cm^2$
• C. $139 \,\Omega^{-1} cm^2$
• D. $51\, \Omega^{-1} cm^2$

Answer 1

Answer: (C)

Equivalent conductance is defined as conducting power of all the ions produced by one gram equivalent of electrolyte.
The equivalent weight of
$BaCl _{2}=\frac{\text { molecular weight }}{2}$
$\lambda_{ m }^{\infty}$ for $BaCl _{2}=\lambda_{ m \left( Ba ^{2}\right)}^{\infty}+2 \lambda_{ m \left( Cl ^{-}\right)}^{\infty}$
$\therefore \lambda_{ eq }^{\infty}$ for $BaCl _{2}=\frac{1}{2} \lambda_{ m \left( Ba ^{2-}\right)}^{\infty}+\lambda_{ m \left( Cl ^{-}\right)}^{\infty}$
$=\frac{127}{2}+76$
$=139.5 \,ohm ^{-1} cm ^{2} eq ^{-1}$
The correct answer is $=139.5\, ohm ^{-1} cm ^{2} eq ^{-1}$