Introduction to Gibbs free energy | Applications of thermodynamics | AP Chemistry | Khan Academy
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Gibbs Free Energy (G) is crucial in determining the favorability of a chemical process, with delta G calculated using delta H and delta S. A negative delta G indicates thermodynamic favorability in the forward direction, while a positive delta G implies non-spontaneity in the reverse direction, and at equilibrium, delta G is zero, signifying a balanced process.
Insights
- Delta G determines the direction in which a chemical reaction will proceed: when it's negative, the reaction is spontaneous and proceeds forward; when positive, it's non-spontaneous and goes in reverse; and at equilibrium, delta G is zero, indicating a balanced state.
- Gibbs Free Energy (G) and its change (delta G) are crucial in determining the favorability of a reaction: a negative delta G signifies a thermodynamically favorable process, while a positive value indicates the opposite, with calculations involving standard enthalpy and entropy changes to assess the direction of the reaction.
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Recent questions
What is Gibbs Free Energy?
Gibbs Free Energy, denoted as G, represents the energy available to do work in a system at constant temperature and pressure. It is a thermodynamic potential that combines enthalpy and entropy to predict whether a reaction will be spontaneous or non-spontaneous.
How is delta G calculated?
Delta G, the change in Gibbs Free Energy, is calculated using the formula delta G = delta H - (T * delta S), where delta H is the change in enthalpy, T is the temperature in Kelvin, and delta S is the change in entropy. This equation helps determine the spontaneity of a reaction based on the energy changes involved.
What does a negative delta G indicate?
A negative delta G value indicates that a process is thermodynamically favorable in the forward direction. This means that the reaction is spontaneous, and the products are more stable than the reactants. The system will naturally move towards this state without requiring external energy input.
What happens at equilibrium in terms of delta G?
At equilibrium, the delta G value is zero, signifying a balanced state where the forward and reverse reactions occur at equal rates. The concentrations of reactants and products remain constant, and there is no net change in the system. This dynamic balance is crucial for understanding the behavior of chemical reactions.
How is delta G naught calculated for a reaction?
Delta G naught for a reaction is calculated using standard enthalpy and entropy changes under standard conditions. A negative delta G naught value indicates that the reaction is thermodynamically favorable in the forward direction. This calculation helps predict the spontaneity of a reaction based on the energy changes associated with it.
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Summary
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Understanding Gibbs Free Energy in Thermodynamics
- Gibbs Free Energy is represented by G, and the change in Gibbs Free Energy is denoted as delta G. The formula for delta G is delta H minus (temperature in Kelvin times delta S).
- When delta G is less than zero, a process is favored in the forward direction, indicating thermodynamic favorability. This is often referred to as a spontaneous reaction in textbooks.
- Conversely, when delta G is greater than zero, the process is favored in the reverse direction, leading to the formation of reactants. This is termed as non-spontaneous in the forward direction.
- At equilibrium, when delta G is zero, the process is balanced, and the concentrations of reactants and products remain constant. The standard state for substances involves pure solids or liquids under one atmosphere pressure, pure gases at one atmosphere pressure, and solutions at one Mueller concentration. Calculating delta G naught for a reaction involves using standard enthalpy and entropy changes, with a negative value indicating thermodynamic favorability in the forward direction.
