(a) Describe how you would carry out a series of experiments to determine the molar conductivities (Λm) of an electrolyte at various concentrations, starting with the measurement of conductance. Explain clearly how you would calibrate the apparatus to obtain the cell constant, and how you would use this value in your calculations.
(b) Explain briefly how you would plot the data obtained from the experiments in part (a) graphically to find the value of the limiting molar conductivity (Λm0) of:
(i) a strong electrolyte;
(ii) a weak electrolyte.
(c) The molar conductivity of aqueous potassium perchlorate at 298K has been measured at selected concentrations:
|
c /mol dm-3
|
0.0005
|
0.0050
|
0.0200
|
0.0500
|
0.1000
|
|
Λm /S m2 mol-1
|
0.0139
|
0.0134
|
0.0128
|
0.0122
|
0.0115
|
(i) By means of a suitable graph, estimate the limiting molar conductivity (Λm0) of aqueous potassium perchlorate.
(ii) If the limiting molar ionic conductivity (λ-) of the perchlorate ion is 6.85 x 10-3 S m2 mol-1, calculate that of the potassium ion (λ+).