Chapter 20: Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions

A set of flashcards covering key concepts related to thermodynamics, entropy, free energy, and chemical reactions from Chapter 20.

Thermodynamics

The study of heat, work, and energy changes in a system.

Entropy (S)

A measure of the number of ways energy can be dispersed in a system; indicative of disorder.

Spontaneous Reaction

A reaction that proceeds without continued outside help once initiated.

Nonspontaneous Reaction

A reaction that requires outside support to proceed.

Enthalpy (ΔH)

The heat content of a system; can be exothermic (releases heat) or endothermic (absorbs heat).

Gibbs Free Energy (ΔG)

A thermodynamic quantity that measures the spontaneity of a process and the useful energy available.

Second Law of Thermodynamics

The entropy of the universe increases in a spontaneous process.

ΔGo

Standard Gibbs free energy change measured at standard conditions.

Microstates

Different configurations that a system can achieve; higher numbers of microstates correspond to higher entropy.

Free Energy Change (ΔG)

Combines entropy and enthalpy changes to determine spontaneity; negative ΔG indicates a spontaneous process.

Third Law of Thermodynamics

The entropy of a perfect crystal at absolute zero is zero.

Standard Molar Entropies (So)

The entropy values for substances at standard conditions (1 atm, 25 °C).

Reaction Quotient (Q)

The ratio of the concentrations of products to reactants at any point during a reaction.

Equilibrium Constant (K)

The ratio of products to reactants at equilibrium; related to ΔG°.

Phases of Matter and Entropy

Entropy varies with phases: solids have low entropy, liquids have more, and gases have the highest.