Question

Cell constant of a conductivity cell is generally obtained by measuring conductance of aqueous solution of:
(A) $BaC{{l}_{2}}$
(B) $LiCl$
(C) $KCl$
(D) $MgC{{l}_{2}}$

Answer 1

We know that Conductivity is the amount of current carried between two electrodes by a known amount of liquid. The volume between the two electrodes must be precise or exact to determine the amount of current carried between them. This volume is known as cell constant.

Complete step by step solution:
The cell constant of a conductivity cell is the ratio of distance between the electrodes plates to the surface area of the electrode plates. It has a unit per centimeter. It is represented by K. This means that the solution having low conductivity has the electrodes placed together or has larger electrodes so that the cell constant remains less than one. It is clear from the formula that the cell constant is only dependent on the distance between the electrodes and their surface area. It does not change with the following factors:
Temperature of electrolyte there is no change with change in temperature. Electrolytes-there is no change with change in electrolytes. Concentration of electrolyte there is no change with change in concentration of electrolytes.
The cell constant is a factor that is used to convert the measured conductance to conductivity.
$Conductivity\times \left( S\cdot c{{m}^{-1}} \right)=cell\text{ }constant\text{ }\left( c{{m}^{-1}} \right)\times conductance\left( S \right)~$
It is determined by the geometry of the cell, but in practical terms can only be measured using a standard of known conductivity, for example $KCl$ which is strong electrolyte. If we change the concentration of electrolyte, it does not affect the cell constant because the cell constant depends only on the area and distance between the electrodes. -So, we can change the concentration of the electrolyte but by keeping it in the right distance.
Hence, option C is correct.

Note:
Remember that the value of cell constant (k) is less than one when the conductivity of an electrode is high. Whereas if the conductivity of an electrode is low then the value of conductivity can raise up to one. When two electrodes are placed close to each other, then the conductivity of the electrodes is high. Whereas when the electrodes are kept far from each other then the ability to conduct becomes low.