TITLE:
Energetic and Entropic Changes in Volume Work and Chemical Reactions
AUTHORS:
Frank Diederichs
KEYWORDS:
Exchanged Entropy, Entropy Production, Coupled Reactions, Activated Complexes, Power Output
JOURNAL NAME:
Advances in Chemical Engineering and Science,
Vol.14 No.1,
January
26,
2024
ABSTRACT: In the present study, energetic and entropic changes
are investigated on a comparative basis, as they occur in the volume changes of
an ideal gas in the Carnot cycle and in the course of the chemical reaction in
a lead-acid battery. Differences between reversible and irreversible processes
have been worked out, in particular between reversibly exchanged entropy (∆eS) and irreversibly produced entropy (∆iS). In the partially
irreversible case, ∆eS and ∆iS add up to the sum ∆S for the volume changes of a gas, and only this
function has an exact differential. In a chemical reaction, however,∆eSis independent on
reversibility. It arises from the different intramolecular energy contents
between products and reactants. Entropy production in a partially irreversible
Carnot cycle is brought about through work-free expansions, whereas in the
irreversible battery reaction entropy is produced via activated complexes, whereby a certain, variable fraction of
the available chemical energy becomes transformed into electrical energy
and the remaining fraction dissipated into heat. The irreversible reaction
process via activated complexes has been explained phenomenologically. For a
sufficiently high power output of coupled reactions, it is essential that the
input energy is not completely reversibly transformed, but rather partially
dissipated, because this can increase the process velocity and consequently its
power output. A reduction of the counter potential is necessary for this
purpose. This is not only important for man-made machines, but also for the
viability of cells.