Level: advanced
Reference: Svante Arrhenius, "On the Dissociation of Substances Dissolved in Water," Zeitschrift für physikalische Chemie 1, 631-48 (1887)
Notes: Svante Arrhenius (1859-1927) is best known to chemists for his work on electrolyte solutions and kinetics. He also attempted to model the influence of atmospheric carbon dioxide on climate (a phenomenon now known as the greenhouse effect). He was awarded the Nobel Prize in chemistry in 1903.
The terminology employed by Arrhenius can be a bit confusing to a modern student of physical chemistry. Arrhenius called the quantity α the "activity coefficient," but it is not the same thing that modern physical chemistry texts call the activity coefficient (following G. N. Lewis). To make matters more confusing, a modern physical chemist might recognize that the Arrhenius α, derived from conductance measurements, combines effects of dissociation and ionic activity in the modern sense. For weak electrolytes, α represents the dissociation ratio to a good approximation, and we may neglect ionic activity coefficients. (See Arrhenius weak electrolyte exercise.) For strong electrolytes at the concentrations mentioned here, ionic activities are quite important. (See Arrhenius strong electrolyte exercise.)
This exercise walks the student through a derivation of a theoretical relationship between α and i, developed by Arrhenius in this paper. Since α and i can be measured independently (from conductance and freezing-point depression experiments respectively), one can compare i from freezing-point depression experiments with i computed from its relationship with α. This comparison was an important part of Arrhenius's paper, where it served as a check on the validity of the hypothesis of electrolyte dissociation.
Solutions: To download solutions, go to:
http://web.lemoyne.edu/giunta/classicalcs/arrcollig.doc
|
| Back to the Classic Calculations home page |
| Back to the top of the Classic Chemistry site |