General Chemistry 2 Study Guide: Gibbs Free Energy and Reaction Direction

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What is the result of the entropy of a closed system over time?

It increases

What is the direction of heat flow in a spontaneous process according to the second law of thermodynamics?

From a hot object to a cold object

What is the measure of the degree of disorder in a system?

Entropy (S)

What is the prediction of a process with a ΔG value of less than 0?

Spontaneous process

What is the condition for a reaction to be spontaneous at all temperatures?

∆H must be negative and ∆S must be positive

What is the result of arranging books in a shelf by height in terms of entropy?

The entropy remains unchanged

What is the significance of ∆G = 0 in a reaction process?

The reaction is at equilibrium

What is the effect of an endothermic process on the enthalpy change (ΔH)?

It increases

What is the unit typically used for Gibbs free energy?

Joules (J)

What happens to ∆G when a reaction is at equilibrium?

∆G = 0

What is the correct equation for Gibbs free energy?

∆G = ∆H – T∆S

What indicates a spontaneous reaction according to Gibbs free energy?

Negative ∆G

Study Notes

The Second Law of Thermodynamics

  • The second law of thermodynamics states that the entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process.
  • Entropy is a measure of the disorder or randomness in a system.
  • Heat always flows from a hot object to a cold object, which is consistent with the second law of thermodynamics.

Entropy and Its Implications

  • In a closed system, entropy increases over time.
  • Some energy transformations are irreversible, which is an implication of the second law of thermodynamics.
  • Entropy is often referred to as the measure of disorder.

Predicting Spontaneity of a Process

  • The thermodynamic quantity used to predict the spontaneity of a process is Gibbs free energy (∆G).
  • At equilibrium, the value of ∆G for a process is zero.
  • ∆G < 0 shows a spontaneous process at a constant temperature and pressure.

Gibbs Free Energy and Its Relationship

  • The equation ∆G = ∆H – T∆S correctly represents the relationship between Gibbs free energy, enthalpy, and entropy.
  • Joules (J) is the unit typically used for Gibbs free energy.
  • A spontaneous reaction is indicated by a negative ∆G.
  • Factors that affect the spontaneity of a reaction according to Gibbs free energy include:
    • Temperature (T)
    • Enthalpy change (∆H)
    • Entropy change (∆S)

Gibbs Free Energy Equations

  • The equation ∆G = RT in JK relates to the spontaneity of a process.
  • The equation ∆G = ∆H – T∆S correctly represents Gibbs free energy (∆G).

Examples of Spontaneous and Non-Spontaneous Processes

  • Rusting of iron is an example of a spontaneous process.
  • Melting of ice cubes at -50C and 1atm is an example of a non-spontaneous process.
  • Ice formation is another example of a non-spontaneous process.
  • Arranging books in a shelf by height does not show an increasing entropy.
  • A type of process that absorbs heat from the surroundings is endothermic.

Test your understanding of Gibbs free energy and its relation to reaction direction, equilibrium, and spontaneity. Learn how to use ∆G to determine the direction of a reaction and understand the significance of ∆G = 0. This quiz covers the fundamental concepts of thermodynamics in general chemistry.

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