Question

Cell constant has unit:
A. ${\text{S}}{{\text{m}}^{ - 1}}$
B. \[{\text{m}}{{\text{S}}^{ - 1}}\]
C. \[{{\text{m}}^{ - 1}}\]
D. \[{{\text{m}}^{ - 2}}\]

Answer 1

Hint: Electrical conductivity can be measured by cell constant. It is connected with the electrodes. It is usually measured from the resistance of the cell. \[{\text{KCl}}\] solution is used for measuring resistance whose conductivity is known.

Complete step by step solution:
Electrochemistry deals with the study of physical and chemical processes in which electricity is either produced or consumed. Passing of electricity through a solution of an electrolyte makes the redox reactions give rise to the phenomenon of electrolysis. The arrangement is called an electrolytic cell. Faraday’s law explains the relationship between the amount of electricity passed and the amount of substance deposited at the electrode.
An electrochemical cell is made from two electrodes. Both electrodes are kept in the same container of molten electrolyte. One is called cathode and the other is anode. Anode is positive and cathode is negative. Reduction occurs in cathode and oxidation occurs in anode. A salt-bridge is connected so that the ions can be passed. A wire completes the external circuit through which the electrons flow.
Cell constant is the ratio of distance between two electrodes to the area of cross-section of the electrode.
It is denoted by \[{{\text{G}}^ * }\].
From the definition, \[{{\text{G}}^ * } = \dfrac{{\text{l}}}{{\text{A}}}\], where \[{\text{l}}\]is the distance between two electrodes.
\[{\text{A}}\]is the area of cross-section of the electrode.
Distance has unit \[{\text{m}}\]and area has unit \[{{\text{m}}^2}\].
Therefore \[{{\text{G}}^ * } = \dfrac{{\text{m}}}{{{{\text{m}}^2}}} = \dfrac{1}{{\text{m}}} = {{\text{m}}^{ - 1}}\]
Therefore the cell constant has unit \[{{\text{m}}^{ - 1}}\].
Therefore the option c is correct.

Additional information:
Faraday’s first law of electrolysis tells that quantity of electricity passed is directly proportional to the amount of substance deposited. Faraday’s second law of electrolysis states that when the same amount of electricity is passed through a number of electrolytic solutions connected in series, masses of the substance deposited is directly proportional to the equivalent weight.

Note: Electrochemical cells are different from electrolytic cells. Electrochemical cells convert chemical energy to electrical energy. Electrolytic cells convert electrical energy to chemical energy. External battery is connected to supply electrons which come through the cathode and go out through anode.