Thermodynamics and Kinetics of Materials Flashcards

The Gibbs free energy change (ΔG) for a reaction at constant temperature and pressure determines spontaneity. Which condition indicates a spontaneous process?

Answer: ΔG < 0

A negative ΔG (ΔG < 0) means the process releases usable energy and proceeds spontaneously at constant T and P.

According to the Gibbs phase rule, for a binary system at equilibrium, the number of degrees of freedom F is given by:

Answer: F = C - P + 2

The Gibbs phase rule is F = C - P + 2, where C is the number of components and P is the number of phases.

Which thermodynamic quantity directly relates the chemical potential of a component to its activity in a solution?

Answer: μ = μ° + RT ln(a)

The chemical potential μ equals the standard chemical potential μ° plus RT times the natural log of activity a.

For an ideal solution of two metals, the enthalpy of mixing (ΔH_mix) is:

Answer: Zero

In an ideal solution, interactions between unlike atoms are identical to like-atom interactions, so ΔH_mix = 0 and mixing is driven entirely by entropy.

The Clausius-Clapeyron equation describes the relationship between pressure and temperature along a phase boundary. For most metals, the solid-liquid boundary has a slope (dP/dT) that is:

Answer: Positive and very steep

For most metals, the solid is denser than the liquid, giving a large positive dP/dT slope on the solid-liquid phase boundary.

Which expression correctly defines the equilibrium constant K for a chemical reaction in terms of standard Gibbs free energy change ΔG°?

Answer: ΔG° = -RT ln K

The standard Gibbs free energy change is related to the equilibrium constant by ΔG° = -RT ln K.

In a regular solution model, the excess Gibbs free energy (G^E) compared to an ideal solution is attributed to:

Answer: Excess enthalpy of mixing only

In the regular solution model, the excess entropy is assumed to be zero and G^E arises solely from a non-zero enthalpy of mixing.