Thermodynamics, Entropy, and Free Energy in Chemical Reactions

What is the difference between spontaneous and nonspontaneous processes?

Spontaneous processes can occur without outside intervention, while nonspontaneous processes require external influence.

What does thermodynamics study?

Thermodynamics studies the spontaneity of reactions, not to be confused with kinetics, which studies the rate of reactions.

What does the second law of thermodynamics state?

The second law states that for any spontaneous process, the entropy of the universe increases.

How is entropy (S) defined?

Entropy is proportional to the number of energetically equivalent ways in which the components of a system can be arranged and measures energy dispersal per unit temperature.

What happens to the entropy of a substance when it changes state from solid to liquid?

The entropy of the substance increases.

What is the relationship between the change in enthalpy (ΔH) and the entropy of the surroundings (ΔS_surr)?

The entropy of the surroundings increases when ΔH_sys is negative (exothermic reactions).

What is Gibbs free energy (G)?

Gibbs free energy is a thermodynamic function that is proportional to the negative of the change in the entropy of the universe.

What does a negative ΔG indicate?

A negative ΔG represents a spontaneous reaction.

How can we calculate the value of ΔG for a reaction?

ΔG can be calculated using the equation ΔG = ΔH - TΔS.

What is the standard change in entropy for a reaction?

It is calculated by subtracting the sum of the standard entropies of the reactants from the sum of the standard entropies of the products, multiplied by their stoichiometric coefficients.

What is the third law of thermodynamics?

The third law establishes that the entropy of a perfect crystal at absolute zero is zero.

What is the equation for the change in Gibbs free energy (ΔG) under nonstandard conditions?

ΔG_rxn = ΔG°_rxn + RT ln Q.

How is the free energy change related to the equilibrium constant (K)?

Under standard conditions, ΔG°_rxn is directly proportional to the negative natural log of K.

What factors affect the entropy of a substance?

Factors include the state, size, and molecular complexity of the substance.

What is the relationship between ΔH, ΔS, and temperature in determining spontaneity?

At low temperatures, a negative ΔH and positive ΔS indicate spontaneity; at high temperatures, a positive ΔS can also indicate spontaneity.

What is the formula for calculating the change in entropy (ΔS)?

ΔS = S_final - S_initial.

What is the significance of a positive ΔG?

A positive ΔG indicates a nonspontaneous reaction.

What is the formula for calculating the standard change in entropy (ΔS°)?

ΔS° = ΣnS(products) - ΣnS(reactants).

What does the equation ΔG = ΔH - TΔS represent?

It represents the relationship between Gibbs free energy, enthalpy, and entropy.

What is the significance of the magnitude of a negative ΔG?

It represents the theoretical amount of energy available to do work.

What happens to the entropy of the surroundings when a system undergoes an exothermic reaction?

The entropy of the surroundings increases.

What is the formula for the change in entropy of the surroundings (ΔS_surr)?

ΔS_surr = -ΔH_sys / T.

What does the term 'energy dispersal' refer to in thermodynamics?

Energy dispersal refers to the distribution of energy among the components of a system, which is quantified by entropy.