Conductance of Solutions

In this experiment you will learn about the electrical conduction properties of aqueous solutions.

Preparation

  1. Objectives and procedure:
    1. What are the two main objectives of the experiment?
    2. There are several steps needed to achieve these objectives. What are they, what are their objectives and how will each step contribute to the overall objectives?
  2. Theory:
    1. What are the differences between strong and weak electrolytes? How can you measure Λ0 and the equilibrium constant of a weak electrolyte? Give formulae.
    2. Use equations (5), (6) and (11):
      1. Find an exact expression of Walden's rule that does not include Λ0.
      2. Derive an expression for the radius of a positive ion. Pay attention to units!
      3. There are two unwanted electrochemical processes in our experiment: double layer formation and faradaic reactions. Explain their origin and the measures we will take to reduce their effects.
  3. Experimental setup:
    1. Draw a schematic of the 2-electrodes and 4-electrodes experimental setups. Explain their advantages and disadvantages.
    2. Estimate the cell constant. Assume that the cell is a cylinder of diameter 1.7 cm and the electrodes are 1 cm apart.
  4. Expected results: (Use the CRC pages found in the literature section to get the necessary values)
    1. Find the specific conductivity, κ, of 6-7 different concentration of KCl between 0.1M and 0.001M.
    2. Find the expected values of Λ0 of HCl, NaCl, sodium acetate and acetic acid. Find the equilibrium constant of acetic acid as well.
    3. Find the ionic radii and specific equivalent conductivity at infinite dilution, λ0±, of Na+, K+ and Cl-.