General Chemistry Chapter 7: Thermochemistry Flashcards
(24 cards)
Isolated systems
exchange neither matter nor energy with the environment
Closed systems
exchange energy, but not matter with the environment
Open systems
exchange both energy and matter with the environment
Isothermal processes
Occur at a constant temperature
Adiabatic processes
exchange no heat with the environment
Isobaric processes
occur at a constant pressure
Isovolumetric (isochoric)
occur at a constant volume
State functions
describe the physical properties of an equilibrium state; they are pathway independent and include pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy and entropy
Standard conditions
defined as 298 K, 1 atm and 1 M concentrations
Standard state
It’s most prevalent from under standard conditions; standard enthalpy, standard entropy and standard free energy are all calculated under standard conditions.
At temperatures about the critical point:
liquid and gas phases are indistinguishable.
Triple point
All three phases of matter exist in equilibrium
Phase diagram
graphs the phases and phase equilibria as a function of temperature and pressure
Temperature
a scaled measure of the average kinetic energy of a substance
Heat
The transfer of energy that results from differences of temperature between two substances.
Enthalpy
The measure of the potential energy of a system found in intermolecular attractions and chemical bonds
Hess’s law
states that the total change in potential energy of a system is equal to the changes of potential energies of the individual steps of the process
Entropy
While often though of as disorder, it is a measure of the degree to which energy has been spread throughout a system or between a system and its surroundings
What is the units for Entropy?
heat transferred per mole per unit K
When in entropy maximized?
at equilibrium
G
reaction proceeds forward (spontaneous)
G = 0
reaction is in dynamic equilibrium
G > 0
reaction proceeds in reverse direction (nonspontaneous)
What does Gibbs depend on?
temperature; can change between spontaneous and non-spontaneous based on temp.
