Thermodynamics & Spontaneity

A collection of flashcards summarizing key concepts in Thermodynamics and Spontaneity.

What defines a spontaneous process in thermodynamics?

A spontaneous process occurs under specified conditions without outside intervention.

What characterizes a nonspontaneous process?

A nonspontaneous process occurs only when energy is continually added to the system.

How does spontaneity relate to the change in entropy of the universe?

For a process to be spontaneous, the change in entropy of the universe (ΔSuniv) must be positive.

What is the relationship between exothermic reactions and spontaneity?

Processes that decrease the energy of the system, such as exothermic reactions, are often spontaneous.

What is entropy and how is it measured?

Entropy (S) is a measure of how spread out or dispersed a system's energy is at a specific temperature.

According to the Second Law of Thermodynamics, what must be true for a process to be spontaneous?

The entropy of the universe (ΔSuniv) must be greater than zero, indicating an increase in overall entropy.

What is the Third Law of Thermodynamics?

A perfect crystal has zero entropy at absolute zero.

What are standard conditions for measuring standard entropy (S°)?

1 atm for gases, pure solids or liquids, and 1 M concentrations for solutions.

How does the freedom of motion impact the standard entropy of substances?

Entropy increases as the freedom of motion of molecules increases, with gases having the highest entropy followed by liquids and solids.

What is Gibbs Free Energy (ΔG) and its significance?

Gibbs Free Energy (ΔG) is the maximum energy that can be released by a process occurring at constant temperature and pressure, indicating spontaneity.

What are the criteria for a reaction to be spontaneous regarding ΔG?

A reaction is spontaneous if ΔG < 0, nonspontaneous if ΔG > 0, and at equilibrium if ΔG = 0.

What is the formula to calculate the standard free energy change for a reaction?

ΔG° rxn = ΣnΔG° f (products) - ΣnΔG° f (reactants).

How does temperature affect entropy during phase changes?

During a phase change, entropy changes can be calculated using the formula ΔS = ΔH/T.

What is the significance of the equilibrium constant (K) in relation to Gibbs Free Energy?

At equilibrium, ΔG = 0 and ΔG° relates to K through the equation ΔG° = -RT ln K.

What is the relationship between reaction spontaneity and the number of gas molecules?

Reactions that increase the number of gas molecules generally result in a positive change in entropy (ΔSsys), indicating greater spontaneity.

In what condition does a reaction with positive ΔH and ΔS become spontaneous?

It can only be spontaneous at high temperatures.

What is the effect of solvation/hydration on the entropy of a solvent?

Solvation/hydration tends to cause a decrease in the entropy of the solvent.

What does a positive ΔSuniv indicate about a process?

A positive ΔSuniv indicates that the process is spontaneous.

What conditions apply to a substance’s standard entropy (S°) when comparing allotropes?

The more mobile the atoms in an allotrope, the greater the standard entropy (S°).