CH353
- Physical Chemistry I Spring 2012, Unique 52135 Lecture Summary, 15 February 2012 |

Entropy
based on configurations: Today we
continued our discussion of entropy based on the number of
configurations available to a thermodynamic system. We derived
an expression for increasing entropy with increasing volume.
We also saw explicitly that the third law of thermodynamics is a
direct consequence of Boltzmann's formulation for entropy. At
0 K, a perfectly pure crystalline substance has only one possible
configuration of the atoms in the crystal, and therefore the molar
entropy of the system is 0.Refocus on the system: Although the 2nd law
provides us with a convenient definition of the direction of
spontaneous change, it is cumbersome to have to quantify what is
going on in the surroundings as well as the system. We would
like to be able to focus only on the system. So we derived an
expression to combine information on changes in energy and change in
entropy during a thermodynamic transformation:d G = dH - TdSFurthermore, we found that if we apply our 2nd law condition of a spontaneous process, we saw that d G < 0, the process
will proceed without any additional input of work. |