Gibbs free energy of formation (ΔGf°) is crucial for understanding the spontaneity and energy dynamics of chemical reactions. It measures the energy change when a substance forms from its elements at standard conditions. The relationship between ΔGf°, enthalpy (ΔHf°), and entropy (S°) is key in determining whether a reaction is exergonic or endergonic. Reference tables for ΔGf° values aid in these calculations, exemplified by the formation of water and ammonia.
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Gibbs free energy is a thermodynamic function that predicts the direction of chemical reactions under constant pressure and temperature conditions
Definition of Standard Gibbs Free Energy of Formation
The standard Gibbs free energy of formation (ΔGf°) quantifies the energy change when one mole of a substance is formed from its elements in their standard states at 1 bar of pressure and 298.15 K (25 °C)
Calculation of Standard Gibbs Free Energy of Formation
The standard Gibbs free energy of formation is determined by the equation ΔGf° = Σ ΔGf°(products) - Σ ΔGf°(reactants), where the summation (Σ) denotes the sum of standard Gibbs free energies for all products minus that of the reactants
Definition of Enthalpy and Entropy
Enthalpy (ΔHf°) is the heat change at constant pressure, and entropy (S°) is the measure of disorder or randomness
Equation Relating Gibbs Free Energy, Enthalpy, and Entropy
The relationship is defined by the equation ΔGf° = ΔHf° - TΔSf°, with T representing the absolute temperature in Kelvin
Spontaneity refers to the tendency of a reaction to occur without external influence
A negative ΔGf° indicates a spontaneous reaction, while a positive ΔGf° suggests a non-spontaneous reaction
The sign of ΔGf° is crucial for predicting the direction and spontaneity of chemical processes
Standard Gibbs free energy of formation tables and charts are indispensable references for chemists, providing ΔGf° values for a multitude of substances and facilitating the calculation of energy changes in reactions
By consulting these materials, one can ascertain the energy involved in the synthesis or decomposition of compounds
The formation of water and ammonia serve as practical examples, showcasing the application of these principles in chemical energetics
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The ______ free energy, symbolized as (G), is used to determine the ______ of chemical reactions at constant pressure and temperature.
Gibbs
direction
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Equation for standard Gibbs free energy of formation (ΔGf°)
ΔGf° = Σ ΔGf°(products) - Σ ΔGf°(reactants)
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Significance of negative ΔGf°
Indicates spontaneous reaction, energy released (exergonic)
