General Chemistry Ch 7. Thermochemistry Flashcards
Isolated systems
Exchange neither matter nor energy with the environment
Closed systems
Can exchange energy but not matter with the environment
Open systems
Can exchanged 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 processes
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
298K, 1atm, and 1M concentrations
Standard state
The most prevalent form of an element under standard conditions, where standard enthalpy, standard entropy, and standard free energy are calculated
Phase changes
Exist at characteristic temperatures and pressures
Fusion
aka melting, occurs at the boundary between the solid and the liquid phases
Freezing
aka crystallization or solidification, occurs at the boundary between the solid and the liquid phases
Vaporization
aka evaporation or boiling, occurs at the boundary between the liquid and gas phases
Condensation
Occurs at the boundary between the liquid and the gas phases
Sublimation and deposition
Occur at the boundary between the solid and gas phases
Critical point
If the temperature is above this point, the liquid and gas phases are indistinguishable
Triple point
Point where all three phases of matter exist in equilibrium
Phase diagram
Graphs the phases and phase equilibria as a function of temperature and pressure
Temperature
Scaled measure of the average kinetic energy of a substance
Heat
The transfer of energy that results from differences of temperature between two substances, the heat content of a system undergoing heating, cooling, or phase changes is the sum of all the respective energy changes
Enthalpy
Measure of the potential energy of a system found in intermolecular attractions and chemical bonds, can also be calculated using heats of formation, heats of combustion, or bond dissociation energies
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
A measure of the degree to which energy has been spread throughout a system or between a system and its surroundings, ratio of heat transferred per mole per unit K, maximized at equilibrium
Gibbs free energy
Derived from both enthalpy and entropy values for a given system, change in Gibbs free energy determines whether a process is spontaneous or non spontaneous, depends on temperature meaning temperature dependent processes change between spontaneous and non spontaneous depending on the temp
DeltaG <0
Reaction proceeds in the forward direction (spontaneous)
DeltaG=0
Reaction is in dynamic equilibrium
DeltaG>0
Reaction proceeds in reverse direction (non spontaneous)
