Gibbs free energy

Why do some chemical reactions happen on their own while others need a push? In this episode, we introduce Gibbs free energy, a powerful concept that answers this very question. Building on our understanding of enthalpy from Hess's law and calorimetry, we'll explore the missing piece of the puzzle: entropy, the measure of disorder. You'll learn how the Gibbs free energy equation combines the drive for lower energy (enthalpy) and higher disorder (entropy) to predict whether a reaction will be spontaneous. This episode will equip you with the ultimate tool for forecasting chemical change.

Check your understanding

These are the same multiple-choice questions you will see in the Quiz section after you listen to the episode. Use them here to preview or review the answers.

What is the primary purpose of calculating the change in Gibbs free energy (ΔG) for a chemical reaction?

  1. To determine the final temperature of the reaction mixture.
  2. To calculate the amount of heat absorbed or released by the reaction.
  3. To predict whether the reaction will be spontaneous.
  4. To find the rate at which the reaction occurs.
  5. To measure the change in volume of the system.

A chemical process is found to have a change in Gibbs free energy (ΔG) that is positive. What does this indicate about the process?

  1. The process is at equilibrium.
  2. The process is non-spontaneous and requires energy input to occur.
  3. The process is spontaneous and will proceed on its own.
  4. The process releases a large amount of heat.
  5. The process happens very quickly.

The Gibbs free energy equation, ΔG = ΔH - TΔS, combines two fundamental driving forces of nature. What quantities represent these two forces?

  1. Pressure (P) and Volume (V)
  2. Heat Capacity (C) and Temperature (T)
  3. Change in Enthalpy (ΔH) and Change in Entropy (ΔS)
  4. Mass (m) and a reaction-specific constant (k)
  5. Equilibrium constant (K) and reaction quotient (Q)

Consider a reaction that releases heat (ΔH is negative) but also results in the system becoming more ordered (ΔS is negative). Under what conditions will this reaction be spontaneous?

  1. At all temperatures.
  2. Only at high temperatures.
  3. Only at low temperatures.
  4. Under no conditions; it is never spontaneous.
  5. The spontaneity is independent of temperature.

In the context of thermochemistry, what does the term 'entropy' (S) represent?

  1. The total heat content of a system.
  2. The amount of useful energy available to do work.
  3. A measure of the disorder or randomness of a system.
  4. The speed of molecular motion in a gas.
  5. The amount of heat required to raise the temperature of a substance.

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