(Last Revision: January 31, 1997)
A study is made of strong and weak electrolytes as a function of concentration . The strong electrolyte is HCl while acetic acid serves as the weak electrolyte.
Sime, Rodney J., "Physical Chemistry - Methods, Techniques and Experiments," Saunders Pub., Philadelphia, PA, 1990. p. 558-556.
The conductance of the solutions is measured by means of a Wheatstone Bridge and a conductance cell. The Bridge actually measures resistance which may then be converted into conductance. Strong electrolytes are considered to be completely ionized at all concentrations while the ionization of weak electrolytes depends on the concentration. A degree of dissociation can be computed from the ratio of the conductance at a particular concentration to the conductance at infinite dilution. The ionization constant can then be estimated from the degree of dissociation.
AC Wheatstone Bridge (Conductance Bridge), conductance cell, volumetric pipets and flasks.
Distilled water, 0.1 N HCl, 0.1N acetic acid, KCl solution.
The laboratory procedure is the same as that indicated in Sime's text. The bridge is balanced using an "electronic eye" tube. Balance is indicated by the widest separation of the "V" in the electronic eye. The range should be selected so that the balance occurs at the middle of the dial.
The calculations are those described by Sime. The slopes called for can be determined by using a spreadsheet such as Quattro Pro, Lotus or Excel.
Harned and Owen, "Physical Chemistry of Electrolytic Solutions,"