free energy of formation

Examples of free energy of formation in the following topics:

• Standard Free Energy Changes

  • The standard Gibbs Free Energy is calculated using the free energy of formation of each component of a reaction at standard pressure.
  • In order to make use of Gibbs energies to predict chemical changes, it is necessary to know the free energies of the individual components of the reaction.
  • As with standard heats of formation, the standard free energy of a substance represents the free energy change associated with the formation of the substance from the elements in their most stable forms as they exist under the standard conditions of 1 atm pressure and 298K.
  • Standard Gibbs free energies of formation are normally found directly from tables.
  • The standard Gibbs free energy of formation of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of that substance from its component elements, at their standard states.

• Pressure and Free Energy

  • Gibbs free energy measures the useful work obtainable from a thermodynamic system at a constant temperature and pressure.
  • The Gibbs free energy is the maximum amount of non-expansion work that can be extracted from a closed system.
  • When a system changes from an initial state to a final state, the Gibbs free energy (ΔG) equals the work exchanged by the system with its surroundings, minus the work of the pressure force.
  • As such, it is a convenient criterion of spontaneity for processes with constant pressure and temperature.
  • Therefore, Gibbs free energy is most useful for thermochemical processes at constant temperature and pressure.

• Free Energy

  • Free energy, called Gibbs free energy (G), is usable energy or energy that is available to do work.
  • A measurement of free energy is used to quantitate these energy transfers.
  • Free energy is called Gibbs free energy (G) after Josiah Willard Gibbs, the scientist who developed the measurement.
  • A negative ∆G also means that the products of the reaction have less free energy than the reactants because they gave off some free energy during the reaction.
  • An endergonic reaction will not take place on its own without the addition of free energy.

• Lattice Energy

  • Lattice energy is a measure of the bond strength in an ionic compound.
  • It is defined as the heat of formation for ions of opposite charge in the gas phase to combine into an ionic solid.
  • The negative sign of the energy is indicative of an exothermic reaction.
  • Alternatively, lattice energy can be thought of as the energy required to separate a mole of an ionic solid into the gaseous form of its ions (that is, the reverse of the reaction shown above).
  • In this equation, NA is Avogadro's constant; M is the Madelung constant, which depends on the crystal geometry; z+ is the charge number of the cation; z- is the charge number of the anion; e is the elementary charge of the electron; n is the Born exponent, a characteristic of the compressibility of the solid; $\epsilon _o$ is the permittivity of free space; and r0 is the distance to the closest ion.

• Free Energy and Work

  • The Gibbs free energy is the maximum amount of non-expansion work that can be extracted from a closed system.
  • The Gibbs free energy is the maximum amount of non-expansion work that can be extracted from a closed system.
  • The work is done at the expense of the system's internal energy.
  • The appellation "free energy" for G has led to so much confusion that many scientists now refer to it simply as the "Gibbs energy. " The "free" part of the older name reflects the steam-engine origins of thermodynamics, with its interest in converting heat into work.
  • The impossibility of extracting all of the internal energy as work is essentially a statement of the Second Law.

• Bond Energy

  • Bond energy is the measure of bond strength.
  • Bond energy is a measure of a chemical bond's strength, meaning that it tells us how likely a pair of atoms is to remain bonded in the presence of energy perturbations.
  • Alternatively, it can be thought of as a measure of the stability gained when two atoms bond to each other, as opposed to their free or unbound states.
  • The bond energy is the average of the bond dissociation energies in a molecule.
  • We can apply bond energy values to determine the enthalpy of a compound's formation, $\Delta H_f$, which can be roughly approximated by simply adding tabulated values for the bond energies of all created bonds.

• Organic Acid Metabolism

  • Some microbes are capable of utilizing such compounds as a sole source of energy.
  • Degradation of formate is then catalyzed by formate dehydrogenase (FDH), which oxidizes formate to ultimately yield CO2.
  • Many bacteria are capable of utilizing fatty acids of various tail lengths as sole energy and carbon sources.
  • Free fatty acids are broken down to acetyl-CoA by dedicated enzymes in the β-oxidation pathway.
  • Give examples of types of organic acid metabolism that are used by microorganisms for a sole source of energy

• Bond Enthalpy

  • Enthalpy is a measure of the total heat energy content in a thermodynamic system, and it is practically used to describe energy transfer during chemical or physical processes in which the pressure remains constant.
  • Generally, a positive change in enthalpy is required to break a bond, while a negative change in enthalpy is accompanied by the formation of a bond.
  • In other words, breaking a bond is an endothermic process, while the formation of bonds is exothermic.
  • Notice that the products are free-radicals.
  • Describe the changes in enthalpy accompanying the breaking or formation of a bond

• ATP in Metabolism

  • A living cell cannot store significant amounts of free energy.
  • Excess free energy would result in an increase of heat in the cell, which would lead to excessive thermal motion that could damage and then destroy the cell.
  • ATP is often called the "energy currency" of the cell and can be used to fill any energy need of the cell.
  • The addition of a second phosphate group to this core molecule results in the formation of adenosine diphosphate (ADP); the addition of a third phosphate group forms adenosine triphosphate (ATP).
  • The hydrolysis of ATP produces ADP, together with an inorganic phosphate ion (Pi), and the release of free energy.

• Activation Energy

  • Exergonic reactions have a net release of energy, but they still require a small amount of energy input before they can proceed with their energy-releasing steps.
  • This small amount of energy input necessary for all chemical reactions to occur is called the activation energy (or free energy of activation) and is abbreviated EA.
  • The free energy released from the exergonic reaction is absorbed by the endergonic reaction.
  • Free energy diagrams illustrate the energy profiles for a given reaction.
  • However, the measure of the activation energy is independent of the reaction's ΔG.