Question

What is the cell constant of the conductivity cell (C) ?

• A. $0.385$ cm${}^{-1}$
• B. $3.85$ cm${}^{-1}$
• C. $38.5$ cm${}^{-1}$
• D. $0.1925$ cm${}^{-1}$

Answer 1

The correct option is D $0.1925$ cm${}^{-1}$

For $25\times {10}^{-4}$ (M) $NaCl$ solution,

${\lambda }_m={\lambda }_m^{\infty }-b\sqrt{C}$

${\lambda }_m=127-{10}^3(25\times {10}^{-4}{)}^{1/2}$

${\lambda }_m=127-{10}^3\times 5\times {10}^{-2}$

${\lambda }_m=77$

${\lambda }_m=\frac{1000G\sigma }{M}$

so, $\sigma =\frac{M{\lambda }_m}{1000G}=\frac{M{\lambda }_{m}R}{1000}=\frac{25\times {10}^{-4}\times 77\times 1000}{1000}=0.1925c{m}^{-1}$