Lecture 11

Question 1

Why can we not apply the lattice model to electrolyte solutions

Answer 1

1. interactions are much longer ranged due to the electrostatic interaction between ions
2. since ions on average will be surrounded by counter ions (of opposite charge), random mixing no longer applies

Question 2

What is the derivation for the chemical potential of an electrolyte?

Answer 2

Found in notes on page 1

Question 3

what is the derivation of the Debye-Huckel theory?

Answer 3

Background:

The central idea of the debye-huckle theory is the presence of an ionic atmosphere of negative ions (counterions) around a positive central ion and an ionic atmosphere of positive ions (counterions) around a central negative ion.

The presence of the cloud of counterion generates electric potential at the position of the central ion thereby changing the energy and thus the chemical potential of the central ion

Question 4

What are the applications of the Debye-Huckel theory?

Answer 4

1. dissociation of a weak acid:
   Pka(when y=1) = Pka + 2Az+z-sqrt(I)
2. Solubility of weak electrolytes:

Pks(when y =1) = Pks +vz+z-sqrt(I)

3. The electrochemical cell