Question

(a) Define molar conductivity of a substance and describe how for weak and strong electrolytes, molar conductivity changes with concentration of solute. How is such change explained?

(b) A voltaic cell is set up at 25 oC with the following half cells:

Ag+ (0.001 M) | Ag and Cu2+ (0.10 M) | Cu

What would be the voltage of this cell? (Eocell = 0.46 V)

Answer 1

(a) Molar Conductivity (∧m): It may be defined as the conductance of a solution containing 1 mole of electrolyte such that the entire solution is placed is between two electrodes one centimeter apart.

Molar conductivity increases with decrease in concentration or increase in dilution as number of ions as well as mobility of ions increased with dilution. For strong electrolytes the number of ions do not increase appreciably on dilution and only mobility of ions increases due to decrease in inter-ionic attractions. Therefore Lm increases a little as shown in graph by a straight line. For weak electrolyte the number of ions as well as mobility of ions increases on dilution as shown by curve in the figure.