Question

Read the given passage and answer the question 1 to
5 that follow :
A conductivity cell is used for measuring the resistance of
an ionic solution by using AC souce for passing current.
Resistence of a conductivity cell filled with 0.1 mol L^-1
KCl solution in 100 ohm. The resistance of same cell when
filled with KCl solution having 3.725 g of KCl dissolved
per litre of solution is 520 ohm. The conductivity of 0.1 mol
L^-1 KCl solution is 1.29 sm^-1[Molar mass of KCl = 74.5
g mol^-1]
1. Why we can not use DC source of voltage during the
measurement of resistance of the conductivity cell?
2. What is cell constant of the above conductivity cell?
3. What is the effect of dilution on the conductivity of KC
solution? Why?
4. Write the product of electrolysis on aqueous solution of
KCl.
5. How does molar conductivity vary with dilution and why?​

Answer 1

Explanation:

1.Because of this the dimensions of the wire changes(thermal expansion due to temperature change) and the resistance changes. So the voltage and current readings which you get are not accurate. So due this the resistance changes which changes the conductivity.

2.The cell constant, K, is equal to the distance in cm between the probe's electrodes divided by the surface area of the electrodes in cm

2

. For solutions with low conductivities the electrodes can be placed closer together or made larger so that the cell constant is less than one.

For a particular conductivity cell the cell constant remains same even if-

Electrolyte is changed.

Concentration of electrolyte is changed.

Temperature of electrolyte is changed.

3.The equivalent conductance of strong electrolyte is increased by dilution, because its value is equal to the multiple of Kv and the volume of solution. By making dilution the volume of solution increases which also increase the value of equivalent conductivity.