Thermochemistry & Thermodynamics
60 terms · page 3 of 3
Standard Molar Entropy
Thermochemistry & Thermodynamics
J/(mol·K)
The absolute entropy of one mole of a substance in its standard state at 298 K.
ΔS° = ΣS°(products) − ΣS°(reactants)
Standard State
Thermochemistry & Thermodynamics
Dimensionless
The reference condition of a pure substance at 1 bar pressure and a stated temperature, conventionally 298.15 K.
denoted by °
State Function
Thermochemistry & Thermodynamics
Various
A property whose value depends only on the current state of the system, not on how that state was reached.
ΔX = X_final − X_initial
Surroundings
Thermochemistry & Thermodynamics
Dimensionless
Everything outside the chosen system with which it can exchange energy or matter.
System
Thermochemistry & Thermodynamics
Dimensionless
The specific part of the universe chosen for thermodynamic study, separated from everything else by a real or imaginary boundary.
Thermochemical Equation
Thermochemistry & Thermodynamics
kJ/mol
A balanced chemical equation that also states the enthalpy change for the amounts shown.
aA + bB → cC, ΔH = x kJ
Thermodynamic Equilibrium
Thermochemistry & Thermodynamics
kJ/mol
The state in which a system's properties no longer change with time and all driving forces are balanced.
ΔG = 0
Thermodynamics
Thermochemistry & Thermodynamics
J
The branch of science dealing with energy, its transformations, and the direction in which processes occur.
Third Law of Thermodynamics
Thermochemistry & Thermodynamics
J/(mol·K)
The entropy of a perfect crystalline substance approaches zero as the temperature approaches absolute zero.
S → 0 as T → 0 K
Trouton's Rule
Thermochemistry & Thermodynamics
J/(mol·K)
The empirical observation that the entropy of vaporisation of many liquids is close to 88 J/(mol·K) at their boiling point.
ΔS_vap = ΔH_vap / T_b ≈ 88
Work
Thermochemistry & Thermodynamics
J
Energy transferred when a force moves through a distance, most often in chemistry as a gas expanding against external pressure.
w = −p_ext ΔV
Zeroth Law of Thermodynamics
Thermochemistry & Thermodynamics
K
If two systems are each in thermal equilibrium with a third, they are in thermal equilibrium with each other.
T_A = T_C and T_B = T_C ⟹ T_A = T_B