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Electrochemistry

Question
CBSEENCH12006061

How is cell constant related to specific conductance of electrolyte?

Solution
Specific conductance or conductivity:

The resistance of any conductor varies directly as its length (l) and inversely as its cross-sectional area (A), i.e.,

Mathematically 

straight R space proportional to space l
R italic proportional to italic 1 over A
italic rightwards double arrow italic space R italic space italic equals italic space rho l over A

Where ρ is called the specific resistance.

l/A is known as cell constant.

If l = 1 cm and A = 1 cm2, then

R = ρ 

The specific resistance is, thus defined as the resistance of one-centimetre cube of a conductor.

The reciprocal of specific resistance is termed the specific conductance or it is the conductance of one-centimetre cube of a conductor.

It is denoted by the symbol κ.

Thus, 
straight kappa space equals 1 over straight rho

Where (κ) kappa →  the specific conductance             

Specific conductance is also called conductivity.

Further,

straight rho space equals space fraction numerator straight A space straight x space straight R over denominator l end fraction
rightwards double arrow 1 over straight rho space space equals space l over straight A space straight x 1 over straight R
rightwards double arrow space straight kappa space equals space l over straight A space straight x space straight C

or  Specific conductance = Conductance × cell constant

In the case of electrolytic solutions, the specific conductance is defined as the conductance of a solution of definite dilution enclosed in a cell having two electrodes of unit area separated by one centimetre apart.

Unit of specific conductance: Ω-1  cm-1