Chemical Thermodynamics

Flashcards covering chemical thermodynamics including spontaneity, entropy, the second law of thermodynamics, and Gibbs Free Energy.

Spontaneous Process

A physical or chemical change that occurs by itself without the application of energy, often characterized by a negative change in free energy ($-\Delta G$).

Nonspontaneous Process

A process that needs the use of energy to occur and only proceeds if work is done, characterized by a positive change in free energy ($+\Delta G$).

Rusting

An example of a spontaneous exothermic process.

Ice Melting

An example of a spontaneous endothermic process.

System

Any part of the universe that we wish to study, which may be separated from the rest of the universe by a real or imaginary boundary.

Surroundings

Everything outside the system in the context of thermodynamic studies.

Universe

The entirety of the system and the surroundings combined.

Entropy ($S$)

A thermodynamic quantity that measures the randomness, disorder, or the number of ways the energy of a system can be dispersed through the motions of its particles.

SI Unit of Entropy

Joules per Kelvin ($J/K$).

State Function

A property whose value depends only on the present state of the system and not on the manner by which that state was reached.

Molar Entropy of the Gaseous State

The highest state of molar entropy for a substance compared to the solid and liquid states.

Molar Entropy of the Solid State

The lowest state of molar entropy for a substance compared to the liquid and gaseous states.

Entropy Change Formula ($\Delta S$)

$\Delta S = S(\text{final state}) - S(\text{initial state})$.

Entropy and Heat Transfer Formula

$\Delta S = \frac{q_{rev}}{T}$, where $q_{rev}$ is the heat absorbed or evolved and $T$ is the absolute temperature.

Second Law of Thermodynamics

States that the total entropy of the universe always increases for a spontaneous process, mathematically expressed as $\Delta S_{universe} = \Delta S_{system} + \Delta S_{surroundings} > 0$.

Standard Absolute Entropy Change ($\Delta S^{\circ}_{reaction}$)

$\Delta S^{\circ}_{reaction} = \sum S^{\circ}_{products} - \sum S^{\circ}_{reactants}$.

Gibbs Free Energy ($G$)

A criterion for spontaneity that applies only to the system by combining enthalpy and entropy: $G = H - TS$.

Free Energy Change ($\Delta G$)

A measure of the spontaneity of a process and the amount of energy that can be obtained from it, determined as $\Delta G = G_{final} - G_{initial}$.

Gibbs Equation

$\Delta G = \Delta H - T \Delta S$, used to determine the free energy change at constant temperature and pressure.

Spontaneous ($\Delta G$ value)

The condition of a process where the change in Gibbs Free Energy ($\Delta G$) is negative.

Nonspontaneous ($\Delta G$ value)

The condition of a process where the change in Gibbs Free Energy ($\Delta G$) is positive.

Equilibrium ($\Delta G$ value)

The state of a system when the change in Gibbs Free Energy ($\Delta G$) is equal to zero.

Standard Free Energy of Reaction (Summation Formula)

$\Delta G^{\circ}_{reaction} = \sum (\Delta G^{\circ}_{f, products}) - \sum (\Delta G^{\circ}_{f, reactants})$.