Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions

These flashcards cover key concepts, definitions, and formulas related to thermodynamics, specifically focusing on entropy, free energy, and the predictability of chemical reactions.

What is the Second Law of Thermodynamics?

It predicts the direction of spontaneous change, indicating that the entropy of an isolated system tends to increase.

How is entropy (S) calculated in a process?

ΔS = qrev/T, where qrev is the reversible heat flow during the process and T is the temperature.

What does a positive ΔS indicate about a reaction?

It indicates an increase in disorder or randomness in the system.

What is Gibbs free energy (G) used for?

G is used to measure the spontaneity of a process, calculated as G = H - TS.

What does ΔG < 0 signify?

It signifies that a reaction is spontaneous.

What is the relationship between entropy and temperature for a reaction?

S° increases as temperature increases, and it also relates to phase transitions from solid to liquid to gas.

What is the formula for calculating standard entropy of reaction (ΔS°rxn)?

ΔS°rxn = ΣS° products - ΣS° reactants.

For the following reaction, how is ΔG° calculated? NaOH(s) + CO2(g) → NaHCO3(s)

ΔG° = ΣΔG° products - ΣΔG° reactants.

What does a higher K value indicate about a reaction?

It indicates that the products are favored over reactants, meaning the reaction is more likely to occur in the forward direction.

What effect does increasing temperature have on the spontaneity of reactions involving ΔH > 0 and ΔS > 0?

At higher temperatures, such reactions are spontaneous.

What is the significance of the 3rd Law of thermodynamics?

It states that a perfect crystal has zero entropy at absolute zero (0 K).