Ch. 7: Thermochemistry

Isolated: Exchange neither matter nor energy w the environment Closed: Can exchange energy but not matter w the environment Closed: Can exchange both energy and matter w the environment

Isothermal: occur at a constatnt temp Adiabatic: exchange no heat w the environment Isobaric: occur @ constant pressure Isovolumetric (isochoric): occur at a constant volume

Describe the physical properties of an equilibrium state; they are pathway independent and include pressure, density, temp, volume, enthalpy, internal energy, Gibbs free energy, and entropy

Defined as 298 K, 1 atm, and 1 M concentrations

Of an element is its most prevalent form under standard conditions - Standard enthalpy, standard entropy, and standard free energy are all calculated under standard conditions

Exist at characteristic temps and pressures

Fusion (melting) and Freezing (crystallization or solidification) occur at the boundary between the solid and liquid phases

Vaporization (evaporation or boiling) and condensation occur at the boundary between the liquid and the gas phases

Occur at the boundary between solid and gas phases

At temps above the critical point the liquid and gas phases are indistinguishable

All three phases of matter exist in equilibrium

For a sys graphs the phases and phase equilibria as a function of temp and pressure

Scaled measure of avg kinetic energy of a substance

Transfer of energy that results from differences of temp between two substances

Undergoing heating cooling, or phase changes is the sum of all of the respective energy changes

Measure of the potential energy of a system found in intermolecular attractions and chemical bonds

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

Can be calculated using heats of formation, heats of combustion, or bond dissociation energies

Measure of the degree to which energy has been spread throughout a syste or between a system and its surroundings • Ratio of heat transferred per mole per unit kelvin • Maximized at equilibrium

Derived from both enthalpy and entropy values for a given system

Determines whether a process is spontaneous or nonspontaneous 🔺G < 0; reaction proceeds in forward direction (spontaneous) 🔺G = 0; reaction is in dynamic equilibrium 🔺G > 0; reaction proceeds in reverse direction (nonspontaneous)

Gibbs free energy depends on temperature; temperature-dependent processes change between spontaneous or nonspontaneous, depending on the temp