DPs Study Guide to Chapter 17
General Chemistry, 4th Ed.”, Hill, Petrucci, McCreary, and Perry (ISBN 0-13-
This chapter is about entropy, the rest of the story concerning Thermodyamics, ie
the energy relationships involved during a chemical reaction or any process for
Everyone should be interested in this chapter because it explains
why your room gets messy seeming all by itself, why the universe expands, and
why nature (plants and animals) spends a great deal of effort keeping order and
I know I am not suppose to bad mouth the book (a student panel selected the
book, DP is always the last to know), we never make mistakes, that sort of thing
Chapter 17 reads like mumbo-jumbo with equations sprinkled about for
I checked out when I read on page 718: “The true meaning of
entropy still relates to the availability and occupation of energy levels.”
not false, but I would not say that to a freshman chemistry student.
Do you at
this moment have a clear understanding of what an energy level is?
If you do,
you did not get it out of this book, for Hill fails to explain it.
So what are we going to do with this mess?
DP will give some illustrations
about entropy, and then move to free energy, or ΔG which is where we want to
Some processes are spontaneous, you simply put the players
together and changes take place.
This part Hill gets right and you have to pay
Thermodynamics tells you about the future equilibrium of the reaction,
will reactants pile up to a great extent or not?
If you mix two chemicals the
thermodynamics predicts the propensity for reaction, and the extent of the
reaction in this process there will be an energy change.
Kinetics is about how
fast this process of coming to equilibrium comes about.
From experience you
can point to several reactions that you know to be spontaneous: (obviously, most
of you will not have had this much experience)
Exercise 17.1A, Problem 1
You know about enthalpy and work.
The enthalpy has to do with
the kinetic energy or motion of the molecules, work has to do with the transfer of
the enthalpy to mechanical motion.
In this course we set up our experiments so
that we could ignore most of the work by doing everything in an open container at
Even ignoring work, there is another energy factor besides
∆H (read as how the motion of the molecules changed), called entropy, S.
most folks S is about the number of possible arrangements the molecules may
take in a system.
Not only do you have to worry about the enthalpy content, you
also have to worry about the location, and possible locations the molecules may
Now DP has to convince you that there is a relationship between