Gen Chem II: Chapter 17

Vocabulary flashcards based on lecture notes about Thermodynamics, Entropy, Gibbs Free Energy, and Equilibrium.

First Law of Thermodynamics

Energy cannot be created or destroyed; the total energy of the universe cannot change.

Spontaneous Process

A process that occurs under given conditions where the system after reaction has less free energy than before.

Enthalpy (ΔH)

Comparison of the bond energy of the reactants to the products.

Entropy (ΔS)

Relates to the randomness/orderliness of a system.

Exothermic Reaction

A reaction where energy is released; ΔH is negative.

Endothermic Reaction

A reaction where energy is absorbed; ΔH is positive.

Boltzmann Constant (k)

Constant used in the entropy equation: 1.38 x 10-23 J/K.

Microstate

A specific way of arranging the components of a system.

Macrostate

A condition defined by macroscopic properties such as temperature and pressure.

Second Law of Thermodynamics

The total entropy change of the universe must be positive for a process to be spontaneous.

Reversible Process

A process for which ΔS of universe = 0.

Irreversible Process

A spontaneous process for which ΔS of universe > 0.

Gibbs Free Energy (G)

The maximum amount of energy from the system available to do work on the surroundings.

ΔGsys

Change in Gibbs Free Energy of the system, equal to ΔHsys - T ΔSsys.

Third Law of Thermodynamics

For a perfect crystal at absolute zero, the absolute entropy = 0 J/mol-K.

Standard Entropy (So)

Entropies for 1 mole at 298K for a particular state.

ΔS surroundings

The change in entropy of the surroundings; proportional to the magnitude of qsystem.

ΔSuniverse

The total entropy change of the universe; equal to ΔSsystem + ΔSsurroundings.

ΔG < 0

Indicates a spontaneous process.

ΔG = 0

Indicates the reaction is at equilibrium.

Molecular Complexity

Determines which substances in the same phase have higher entropies.

Allotrope

Different structural forms of the same element.

Standard Conditions

Normal state at a specific temperature, partial pressure of gas = 1 atm, concentration = 1M.

ΔG = ΔG° + RTlnQ

Gibbs Free Energy equation under nonstandard conditions.

ΔG° = -RTlnK

Relationship between Gibbs Free Energy and the equilibrium constant at equilibrium.

W (Entropy)

The number of energetically equivalent ways of arranging the components of a system.

Temperature Dependence on K

Increasing the temperature decreases the value of the equilibrium constant for an exothermic reaction.

Temperature Dependence on K

Increasing the temperature increases the value of the equilibrium constant for an endothermic reaction.

Bond Energy

The amount of energy needed to break a bond.

ΔG = ΔH – T(ΔS)

Formula for Gibbs Free Energy