Maharashtra BoardEnglish MediumSTD 12 ScienceChemistryElectrochemistry3 Marks
Question
How is the cell constant of a conductivity cell determined?
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Answer
The cell constant of a given conductivity cell is obtained by measuring the resistance (R) (or the conductance) of a standard solution whose conductivity $(f_c)$ is accurately known by using Wheatstone’s bridge. For this purpose, KCl solution of accurately known conductivity is used.$\kappa_{ KCl }=\frac{1}{R_{ KCl }} \times \frac{l}{a}$ where $\frac{l}{a}$ is a cell constant, represented by $b$.
$
\therefore \kappa_{ KCl }=\frac{b}{R_{ KCl }}
$
or $b = k _{ KCl } \times R _{ KCl }$
For example, the conductivity of $0.01 M KCl$ is $0.00141 \Omega^{-1} cm ^{-1}\left( S cm ^{-1}\right)$. Hence by measuring $R KCl$ the cell constant $b$ can be obtained.
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