Chemistry 2B - Spontaneity, Entropy, and Free Energy

Vocabulary flashcards covering the principles of spontaneity, entropy laws, Gibbs free energy, and equilibrium constants based on Chapter 10 lecture notes.

Spontaneous Process

A process that is capable of proceeding in a given direction without outside intervention, which may occur fast or slow.

Nonspontaneous Process

A process that will not occur without outside intervention; if a forward process is spontaneous, the reverse is always nonspontaneous.

Entropy ($S$)

An extensive state function that measures the probability of the state or randomness of a system; it increases with temperature and as matter spreads out.

Third Law of Thermodynamics

The principle stating that the entropy of a pure perfect crystal at $0\,K$ is zero ($S = 0$).

Entropy Change ($\Delta S$) for Reversible Processes

The heat transferred ($q_{rev}$) divided by the Kelvin temperature ($T$), defined as $\Delta S = \frac{q_{rev}}{T}$.

Second Law of Thermodynamics

States that all spontaneous processes produce an increase in the entropy of the universe ($\Delta S_{univ} > 0$).

Gibbs Free Energy ($G$)

A thermodynamic quantity defined as $G = H - TS$; at constant temperature, the change is $\Delta G = \Delta H - T\Delta S$.

Criteria for Spontaneous Change ($\Delta G$)

A process is spontaneous if $\Delta G < 0$, non-spontaneous if $\Delta G > 0$, and at equilibrium if $\Delta G = 0$.

Standard Molar Entropy ($S^{\circ}$)

An intensive state function representing the entropy of $1\,mol$ of a pure substance in its standard state ($1\,atm$), typically measured in $J\,K^{-1}\,mol^{-1}$.

Standard Gibbs Free Energy of Formation ($\Delta G_f^{\circ}$)

The change in Gibbs free energy for a reaction in which $1\,mole$ of a substance in its standard state is formed from its elements in their standard states.

Thermodynamic Reaction Quotient ($Q_{th}$)

A value that expresses the relative amounts of products and reactants under non-standard conditions, related to $\Delta G$ by the equation $\Delta G = \Delta G^{\circ} + RT\ln(Q)$.

Standard Gibbs Energy Change and Equilibrium ($K$)

The relationship defined by the equation $\Delta G^{\circ} = -RT\ln(K)$, where $K$ is the thermodynamic equilibrium constant.

Van’t Hoff Equation

An equation describing the temperature dependence of the equilibrium constant $K$ relative to $\Delta H^{\circ}$, used to see how $K$ changes with temperature.

Clausius-Clapeyron Equation

A special case of the Van’t Hoff equation that specifically relates the vapor pressure of a substance to its temperature.