Concepts.doc (Word 97)

PV = nRT

For an irreversible expansion against a constant external pressure

For an isothermal reversible expansion,

At constant volume, w = 0; if there is no non-expansion work, then

• Other Topics: thermochemistry

At constant pressure (with no non-expansion work),

• Expansion into a vacuum
• Joule tried to measure the change in temperature with volume at constant U;
• No work was done because the gas was expanding against a vacuum (P_ext = 0, w = 0)
• For an ideal gas, the temperature will not change because no work is done. For a real gas, the temperature will decrease slightly (although Joule was not able to measure any change in temperature because his equipment was not sensitive enough)
• For an ideal gas, m_J = 0

• Expansion at constant H (isenthalpic)
• A gas at high pressure expands through a throttle valve into an area of lower pressure. The container is insulated so that the expansion is adiabatic.
• For an ideal gas, m_J-T = 0
• For real gases, the Joule-Thomson coefficient is a property of the material that depends on temperature and pressure.
• The Joule-Thomson inversion temperature is the temperature above which m_J-T is negative, and below which m_J-T is positive. When m_J-T is negative, the gas will warm upon expansion. When m_J-T is positive, the gas will cool upon expansion.

At constant volume,

At constant pressure,

Similarly,

For an ideal gas:

For mixing, the total entropy change is

and the entropy change per mole of mixture is

For a reversible adiabatic process, DS = 0

At constant P and T … DG < 0

At constant V and T … DA < 0

At constant V and S … DU < 0

At constant P and S … DH < 0

• State vs. path functions
• Exact vs. inexact differentials; Euler's Relation
• Reversible vs. irreversible processes
• Open, closed, isolated systems; homogeneous vs. heterogeneous systems; singular vs. compound systems; partitioned systems; etc.
• Different types of processes: isothermal, isopiestic (isobaric), isochoric, isoenthalpic, isoentropic, adiabatic
• Equipartition of energy, how it is used to predict energies and heat capacities
• Boltzman expression
• Critical V, P, T
• Carnot Cycle
• Clausius Inequality
• Third Law of Thermodynamics

Relevant pages in Mortimer are up to and including Section 5.2.

Note: This list is only a guide to help you study. It is NOT comprehensive, and the exam may cover any topics discussed in class.