ME Thermodynamics and Kinetics of Materials

Question 1

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

Accepted Answer

ΔG < 0

Answer

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

Question 2

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

Accepted Answer

F = C - P + 2

Answer

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

Question 3

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

Accepted Answer

μ = μ° + RT ln(a)

Answer

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

Question 4

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

Accepted Answer

Zero

Answer

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.

Question 5

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:

Accepted Answer

Positive and very steep

Answer

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

ME - Materials Engineer Practice Test

ME - Materials Engineer Practice Test

ME Thermodynamics and Kinetics of Materials