Question

How do you find the cell constant experimentally?

Answer 1

The cell constant is the ratio of conductivity and the conductance. We know that, to determine the cell constant, we have to measure the conductance of the standard solution. We already know the conductivity of the standard solution.

Complete answer:
To find the cell constant, the conductance of the standard solution should be found. Generally, potassium chloride is used as the standard solution whose conductivity at different temperatures and different concentrations is known. For example, if the conductivity of $KCl$ is $0.012$ , then the cell constant will be determined as follows:
We know that cell constant is the ratio of the conductivity and the conductance of the given solution.
Cell constant $= \dfrac{{{\text{conductivity}}}}{{{\text{conductance}}}} = \dfrac{{0.012}}{x}$
This expression gives the value of the cell constant which is then used to calculate the conductivity which can be done either from the conductance or the resistance of the given electrolytic solution. Remember that the electrical resistance is the reciprocal of conductance. That means the product of resistance and conductance is one. To convert resistance into conductance, we have to divide the given resistance by one. Here, we used $KCl$ as the standard solution because it is very stable.

Note:
Note that the cell constant is directly proportional to the distance between the two conductive plates and it is inversely proportional to their surface area. The cell constant can also be defined as the ratio of the length of the given conductor to the area of cross-section of the conductor.