key term - δg = δg° + rt ln q

Definition

This equation relates the Gibbs free energy change (δg) of a reaction to its standard Gibbs free energy change (δg°), temperature (T), and the reaction quotient (q). It highlights how the spontaneity of a reaction can be influenced by both standard conditions and the actual concentrations of reactants and products at any given moment, bridging thermodynamics and chemical equilibria.

5 Must Know Facts For Your Next Test

1. The term δg° represents the Gibbs free energy change under standard conditions, which is crucial for determining whether a reaction is spontaneous at those specific conditions.
2. The term 'rt ln q' adjusts the standard Gibbs free energy change based on the current concentrations of reactants and products, allowing for real-time assessment of reaction spontaneity.
3. When δg is negative, it indicates that a reaction can occur spontaneously in the forward direction; when positive, the reverse reaction is favored.
4. At equilibrium, δg equals zero, which implies that the standard Gibbs free energy change equals rt ln K, connecting standard conditions with equilibrium.
5. This equation illustrates that as q approaches K, the system's Gibbs free energy change approaches zero, indicating the system is moving toward equilibrium.

Review Questions

• How does the equation δg = δg° + rt ln q help us understand the relationship between spontaneity and reaction conditions?
  • The equation illustrates that spontaneity is not just determined by standard conditions represented by δg°, but also depends on the actual concentrations of reactants and products through q. If δg is negative, it suggests that under current conditions, the reaction can proceed spontaneously. Thus, understanding both δg° and how q changes allows us to predict when reactions will occur naturally.
• In what way does this equation link the concepts of equilibrium constants and Gibbs free energy?
  • The equation establishes a direct relationship between Gibbs free energy changes and equilibrium constants by showing that at equilibrium (where δg = 0), δg° equals rt ln K. This means that the standard free energy change can be calculated using the equilibrium constant. Thus, understanding one allows us to derive information about the other, reinforcing their interconnectedness in thermodynamics.
• Critically evaluate how varying temperature might affect the spontaneity of a reaction according to this equation.
  • Varying temperature influences the term 'rt ln q' significantly since both r (the gas constant) and T (temperature in Kelvin) are directly involved. An increase in temperature can either favor or hinder spontaneity depending on whether a reaction is exothermic or endothermic. For endothermic reactions, higher temperatures might lead to more negative values of δg due to an increase in T, thereby potentially promoting spontaneous behavior. This critical evaluation highlights how temperature acts as a key factor in determining how far a reaction moves toward equilibrium based on Gibbs free energy.

Related terms

Gibbs Free Energy:

A thermodynamic potential that measures the maximum reversible work obtainable from a system at constant temperature and pressure.

Reaction Quotient (q): A ratio of the concentrations of products to reactants at any point in a reaction, not necessarily at equilibrium.

Equilibrium Constant (K): The ratio of the concentrations of products to reactants at equilibrium, specific to a given reaction at a certain temperature.