Thermodynamics and Equilibrium

A set of flashcards covering key concepts related to thermodynamics and equilibrium in chemistry.

Entropy

A thermodynamic quantity that measures the dispersion of energy in a system.

Gibbs Free Energy (G)

A thermodynamic quantity defined as G = H - TS, used to determine spontaneity of a reaction.

First Law of Thermodynamics

The change in internal energy (ΔU) of a system equals the sum of heat (q) and work (w) done.

Second Law of Thermodynamics

The total entropy of a system and its surroundings always increases for a spontaneous process.

Spontaneous Process

A physical or chemical change that occurs by itself without outside force, continuing until equilibrium is reached.

Free Energy Change (ΔG)

Can be used to determine if a reaction is spontaneous; ΔG < 0 indicates spontaneity.

Sign Convention for q

q is negative when heat is evolved by the system and positive when heat is absorbed by the system.

Criterion for Spontaneous Reaction

The increase in entropy of the system and its surroundings must be positive (ΔS > 0).

Third Law of Thermodynamics

A perfectly crystalline substance at zero Kelvin has an entropy of zero.

Entropy Change (ΔS) for Reactions

Entropy usually increases when a molecule breaks into smaller molecules, the number of gas moles increases, or solid changes to liquid or gas.

Standard Free Energy Change (ΔG°)

The free energy change that occurs when 1 mol of substance is formed from its elements in standard states.

Heat Capacity at Constant Pressure (qP)

The heat absorbed or evolved at constant pressure, expressed as qP = ΔH.

Entropy as a State Function

Entropy depends on variables such as temperature and pressure determining the state of a substance.

Calculation of Entropy Change

ΔS is calculated using ΔS = Sf - Si, where Sf is the final entropy and Si is the initial entropy.

Work (w) in Thermodynamics

w = -PdV; negative work indicates that the system does work on its surroundings.