Dear Olga,

 The molar conductivity is given by:

Am = k/c

where:

κ is the measured conductivity

c is the electrolyte concentration

This equation can be written as:

f = k x c-1

f'' (x) = -k x c-2 ; therefore, A (x) = -k x c-2 (differential equation)

Please note, that two cases should be distinguished: strong electrolytes and weak electrolytes.

For strong electrolytes, such as salts, strong acids and strong bases, the molar conductivity depends only weakly on concentration. Based on experimental data Friedrich Kohlrausch (around the year 1900) proposed the non-linear law for strong electrolytes:

Am = A0m - K x C1/2

where

A0m is the molar conductivity at infinite dilution (or limiting molar conductivity)

K is the Kohlrausch coefficient, which depends mainly on the stoichiometry of the specific salt in solution.

Hoping this will be helpful,

Rafik

Dear Olga  and prof  Rafik Karaman,

As  prof  Karaman  said:

 The molar conductivity is given by:

Am = k/c

where:

κ is the measured conductivity

c is the electrolyte concentration

This equation can be written as:

f = k x c-1.

f''(x) = -k x c-2 ; therefore, A (x) = -k x c-2 (differential equation)

Here   it is not clear to me  way  f'' (x) .

Perhaps,    f(k,c)=k/c=  k  c-1 is function of two variables k and c. If we for a moment consider that   k is fixed we can   compute the derivative with respect   to c and we get 

f'' (c) = -k  c-2   (the first derivative).    Perhaps, I miss here something.

Please be more specific.

best,

Miodrag

Dear Miodrag,

You do not miss anything. Both k and c are variables.

Rafik