Thermochemistry Flashcards
System
The particular part of the universe being studied
Isolated system
Cannot exchange energy or matter with the surroundings
Closed system
Can exchange energy but not matter with the surroundings
Open system
Can exchange energy and matter with the surroundings
Isothermal process
Systems at constant temperature
Adiabatic process
Systems with no heat exchange
Isobaric process
Systems at constant pressure
Isochoric process
Systems at constant volume
Heat (q)
A form of energy easily transferred to or from a system due to a temperature differences
absorbed = +
lost = -
q = mcT
Specific heat
How much energy it takes to raise the temperature of a material
State function
Properties whose magnitude does not depend on the path of change
P, V, T, H, S, G, U
Standard conditions
298 K
1 atm
1 M concentration
Standard state
A substance in its most stable form under standard conditions
Enthalpy (H)
A process equal to the heat absorbed or given off by the system at constant pressure
Endothermic = +
Exothermic = -
Standard heat of formation
The enthalpy change if one mole of a compound is formed directly from its elements in their standard states
Standard heat of reaction
The enthalpy change when a reaction is carried out under standard conditions
Hess’s Law
Enthalpies of reactions are additive
Bond dissociation energy
The energy required to break a specific chemical bond in one mole of gaseous molecules
Heat of combustion
The heat released for the complete combustion of a compound in its standard state to form stable products in their standard states
Entropy (S)
A measure of disorder of a system
Energy/temp = J/K or cal/K
Second law of thermodynamics
All spontaneous processes proceed such that the entropy of the system plus its surroundings increases
Gibbs free energy
The max amount of energy released by a process occurring at constant temperature and pressure
- = spontaneous
+ = nonspontaneous
0 = equilibrium
Standard free energy
The delta G of a process occurring with reactants in their standard states at standard conditions
Standard free energy of formation
The free energy change when 1 mol of a compound in its standard state is formed from its elements in their standard states under standard conditions
