key term - δg°

Definition

The symbol δg° represents the standard Gibbs free energy change of a reaction, which is a measure of the spontaneity of that reaction under standard conditions. It helps predict whether a reaction will proceed in the forward direction or if it is more likely to be spontaneous in the reverse direction, based on the difference in energy between reactants and products. This value is crucial for understanding the favorability of reactions and is tied to concepts like equilibrium and thermodynamic stability.

5 Must Know Facts For Your Next Test

1. A negative δg° value indicates that the reaction is spontaneous in the forward direction, while a positive value suggests that the reverse reaction is favored.
2. At equilibrium, δg° equals zero, meaning there is no net change in the concentration of reactants and products over time.
3. The standard Gibbs free energy change can be calculated using standard enthalpy and entropy changes with the formula: δg° = δh° - Tδs°, where T is temperature in Kelvin.
4. The sign and magnitude of δg° can provide insights into the relative stability of reactants and products, influencing how reactions are driven.
5. Understanding δg° is essential for predicting the behavior of chemical reactions in various applications, from industrial processes to biological systems.

Review Questions

• How does the value of δg° determine whether a chemical reaction will occur spontaneously?
  • The value of δg° plays a critical role in predicting the spontaneity of a chemical reaction. If δg° is negative, it means that the reaction can proceed spontaneously in the forward direction, as it releases energy. Conversely, if δg° is positive, this indicates that the reverse reaction is more favorable. At equilibrium, when δg° equals zero, both reactants and products are present at constant concentrations, showing no net change.
• Discuss how δg° relates to equilibrium and the concept of reaction spontaneity.
  • δg° is directly related to equilibrium as it provides insight into how far a reaction has proceeded towards completion. When δg° is negative, it indicates that products are favored over reactants, pushing the system towards equilibrium in that direction. As a system approaches equilibrium, the value of δg° decreases until it reaches zero, where reactants and products are balanced. This relationship highlights how spontaneity drives reactions towards their equilibrium state.
• Evaluate how changes in temperature affect the standard Gibbs free energy change (δg°) for a given reaction.
  • Changes in temperature can significantly impact the standard Gibbs free energy change (δg°) for a reaction due to its dependence on both enthalpy and entropy. The equation δg° = δh° - Tδs° illustrates this relationship; as temperature increases, the influence of entropy becomes more pronounced. If δs° is positive (indicating increased disorder), higher temperatures can lead to a more negative δg°, making spontaneous reactions more favorable. Conversely, if δs° is negative, increased temperature may make δg° less favorable. Thus, understanding this temperature dependency is essential for predicting reaction behaviors under varying conditions.

Related terms

Gibbs Free Energy:

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

Spontaneity: The tendency of a reaction to proceed without external intervention, determined by the sign of δg°.

Standard Conditions:

The set conditions (typically 1 atm pressure and 25°C) under which thermodynamic data, including δg°, are usually measured.