THERMODYNAMICS & SPONTANEITY

These flashcards cover key concepts from thermodynamics and spontaneity, focusing on spontaneous processes, entropy, and Gibbs Free Energy.

What is a spontaneous process?

A spontaneous process occurs under a specified set of conditions without outside intervention.

What characterizes a nonspontaneous process?

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

What type of processes are often spontaneous?

Processes that decrease the energy of the system (exothermic) are often spontaneous.

What is the Second Law of Thermodynamics?

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

What does ΔSuniv represent?

ΔSuniv is equal to ΔSsys + ΔSsurr.

What happens to entropy as temperature increases according to the Third Law of Thermodynamics?

Entropy increases as temperature increases.

What is standard entropy (S°)?

Standard entropy (S°) is the entropy of a substance at standard conditions, usually at 1 atm and 298 K.

Which phase typically has the highest entropy?

Gases typically have higher entropy than liquids, which have higher entropy than solids.

What is Gibbs Free Energy (ΔG)?

Gibbs Free Energy (ΔG) is the maximum energy released by a process occurring at constant temperature and pressure, available to do useful work.

What is the relationship between ΔG and spontaneity?

If ΔG < 0, the reaction is spontaneous; if ΔG > 0, the reaction is nonspontaneous; if ΔG = 0, the system is at equilibrium.

What is the formula for calculating standard free energy change (ΔG°)?

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

Which processes indicate an increase in entropy, ΔSsys?

Reactions that increase the number of gas molecules, increase in temperature, vaporization or sublimation, and melting.

How does solvation affect the change in entropy for ionic solutes?

For ionic solutes, solvation can cause entropy of the solvent to decrease, but smaller charged ions are more likely to have a positive ΔSsys.

What is the effect of ΔH and ΔS on spontaneity according to the Gibbs Free Energy relation?

Positive ΔH and positive ΔS can lead to spontaneity only at high temperatures.

What condition must be true for ΔSuniv to indicate spontaneity?

ΔSuniv must be greater than 0 for a process to be spontaneous.

How do we calculate entropy change during a phase change?

ΔS = ΔH / T, where ΔH is the enthalpy change and T is the temperature.