General Chemistry - Thermochemistry

MCAT Chapter 7

System

matter being observed,

surroundings

everything outside the system

Isolated system

The system cannot exchange energy or matter with the surroundings

Closed system

The system can exchange energy but not matter with surroundings

Open System

The system can exchange both energy and matter with the surroudnings

First Law of Thermodynamics

change in internal energy of the system = heat added to the system - work done by the system

Isothermal processes

occur when system’s temperature is constant

Adiabatic process

occurs when no heat is exchanged between the system and the environment, thus thermal energy of system is constant throughout process

Isobaric process

Occur when the pressure of the system is constant

Isovolumerric Process

Experience no change in volume, no work is performed, first law delta U = Q,

Spontaneous process

one that can occur by itself without having to be driven by energy from an outside source

Phase diagrams

graphs that show standard and non standard states of matter for a given substance in an isolated system, as determined by temp and pressures

Evaporation/Vaporization

The process of liquid having enough kinetic energy to leave liquid phase and escapse to gas phase

Boiling

Rapid bubbling of entire liquid with rapid release of liquid as gas particle

Condensation

Gas back to the liquid phase

boiling point

temperature at which vapor pressure of liquid equals ambient pressure

Fusing/melting

transition from solid to liquid

Solidifcation/crystalizaiton/freezing

liquid to solid

sublimiation

solid goes directly into the gas phase

Deposition

gaseous to solid phase

Lines of equilibrium/phase boundaries

lines of phase diagram, indicate temp adn pressure values for equilibria between phases

Triple point

point at which three phase boundaries meet

Critical point

where phase point between liquid and gas terminates

Temperature

related to average kinetic energy of the particles of a substance

Thermal Enthalpy

The average kinetic energy of particles in substance

Heat

Transfer of energy from one substance to another as a result of their difference in temp

Zeroth law of thermodynamics

implies that objects are in thermal equilibrium only when their temperatures are equal

Calorimetry

The process of measuring transferred heat

Specific heat

amount of energy required to raise the temp of one gram of substance by one degree

Standard enthalpy of formation

enthalpy required to produce one mole of a compound from its elements in their standard states

Standard enthalpy of reaction

enthalpy change accompanying a reaciton being carried out under standard conditions

Hess’s Law

Enthalpy changes of reactions are additive

Bond Dissociation energy

Average energy that is required to break a particular type of bond between atoms in gas phase

Standard heat of combustion

enthalpy change associated with combustion of fuel

Second law of thermodynamics

states energy spontaneously disperses from being located to becoming spread out if its not hindered from doing so

Entropy

measure of spontaneous dispersal of energy fat specific temperature

Gibbs free energy

measure of enthalpy and entropy as a system undergoes a process

Exergonic

when a system releases energy

Spontanity if delta g is negative

reaction spontaneous

spontanity if delta g is poistive

nonspontaneous

Outcome when delta H and delta S are positive

spontaneous at high temperatures

Outcome when delta H is positive and delta S is engative

nonspontaneous at all temps

Outcome when Delta H is negative and delta S is negative

spontaneous at all temps

Outcome when delta H and delta S are negative

spontaneous at low temps