Entropy, S, is a thermodynamic term that reflects the
disorder, or randomness, of the system.
The more disordered, or random, the system is, the larger
the value of S.
Entropy is a state function.
It is independent of path.
For a syste
Table I. Fat Analysis of Ruffles Potato Chips
Reduced Fat Baked
Mass of 250mL beaker
Mass of 250mL beaker with chips
Mass of potato chips
Mass of 100mL beaker and boiling beads
September 10th, 2015
Goal Statement: To understand operations of Excel and perform basic laboratory procedures.
Procedure: Chemistry 12901 Lab Manual, Department of C
The Molecular Interpretation of Entropy
Molecular Motions and Energy
The entropy of a system indicates its disorder.
A gas is less ordered than a liquid, which is less ordered
than a solid.
Any process that increases the number of gas molecules
Making Qualitative Predictions About S
Consider the melting of ice.
In ice, the molecules are held rigidly in a lattice.
When it melts, the molecules will have more freedom to
move (increases the number of degrees of freedom).
The molecules are more r
Entropy Changes in Chemical Reactions
Absolute entropy can be determined from complicated
Values are based on a reference point of zero for a
perfect crystalline solid at 0K (the 3rd law).
Standard molar entropy, So is the molar entropy o
Gibbs Free Energy
For a spontaneous reaction the entropy of the universe must
Reactions with large negative H values tend to be
How can we use S and H to predict whether a reaction is
The Gibbs free energy, (free en
Standard Free-Energy Changes
We can tabulate standard free energies of formation, Gf .
Standard states are pure solid, pure liquid, 1 atm (gas), 1 M
concentration (solution), and G = 0 for elements.
We most often use 25oC (or 298 K) as the temperature.
Free Energy and the Equilibrium Constant
Recall that G and Keq (equilibrium constant) apply to
Recall that G and Q (equilibrium quotient) apply to any
It is useful to determine whether substances will react under
Preventing the Corrosion of Iron
Corrosion can be prevented by coating the iron with paint or
This prevents oxygen and water from reacting at the surface
of the iron.
Galvanized iron is coated with a thin layer of zinc.
Zinc protects th
Boltzmanns Equation and Microstates
Statistical thermodynamics is a field that uses statistics and
probability to link the microscopic and macroscopic world.
Entropy may be connected to the behavior of atoms and
Envision a microstate: a snap
Chemical thermodynamics is concerned with energy relationships in
We consider enthalpy.
We also consider entropy in the reaction.
Recall the first law of thermodynamics: energy is conserved.
E= q + w
Chem Study Guide 2015
Matter takes up space
Substances definite composition and properties made from matter Elements/Compounds
Energy stored within molecules bonds in the form of potential energy
Energy never created or destroyed always conserved