Enthalpy, entropy and free energy of formation

Thermodynamic data for COBrF are even more scarce than physical property data. In particular, the enthalpies, entropies, and free energies of formation of the material have been... 

Enthalpy, Entropy, and Free Energy of Formation of CgHjs s ... 

Values for cellular enthalpy, entropy, and free energy of formation. 

Values for the enthalpy, entropy, and free energy of formation of cells from which the ions have been theoretically removed. 

There are extensive tables of thermodynamic data which give standard enthalpies and free energies of formation and entropies in the standard... 

Calculate the standard reaction enthalpy, entropy, and free energy for each reaction from Appendix 2A. For each case, confirm that the value obtained from the free energies of formation is the same as that obtained by using the relation... 

The thermodynamic quantities listed are for one mole of substance in its standard state, that is at 1 atm pressure. The enthalpies and free energies of formation of substances are the changes in those thermodynamic properties when a substance in its standard state is formed from its elements in their standard states. The standard state of an element is its normal physical state at 1 atm, and for the data given in these tables, 298.15 K. The entropies listed are absolute in the sense that they are based on the assumption that the entropy of a pure substance is zero at the absolute zero of temperature. 

The entropies so computed are termed Third Law, absolute, or conventional entropies, and designated S° or. These are not at all comparable to enthalpies and free energies of formation, AfH° and A/G°, which instead refer to reactions forming the compound from its elements. For example, AfH° and AfG° for an element such as 02(5) at 25°C are both necessarily zero, while the absolute entropy, S Igg, is 205.15 mol (see Table 7.1). 

Physical and Thermodynamic Properties of Pure Chemicals Data Compilation This comprehensive data base is designed primarily for the chemical engineer and, consequently, includes many thermodynamic quantities such as enthalpies and free energies of formation, standard entropies, and so on. Molar volume calculated from density, and van der Waal s surface, and volume are also cited. Supplementary updates are published periodically. 

Rand and Kubaschewski have provided a critical assessment of all the available thermochemical data for binary compounds of uranium and a consistent set of values, including in some instances estimates, for enthalpies of formation and standard entropies, enthalpies of transformation, heat capacities, vapour pressures, and free energies of formation. 

The publication of the JANAF thermochemical tables was a project (now terminated) for the provision of data in loose-leaf form with facilities for updating the information from time to time. These Joint Army-Navy-Air Force Tables were prepared by the Dow Chemical Company. The prime quantities tabulated are the heat capacity, entropy, free energy and enthalpy functions , enthalpy and free energy of formation, and the logarithm of the equilibrium constant of formation. The temperature range covered is from zero to several thousand kelvins, and includes values for 298.15 K. 

Let us now try to sketch the behaviour of the enthalpy, entropy and free energy (AfG) as a function of the salt concentration. Upon increasing the ionic strength, a change from exothermic to endothermic behaviour is observed. This means that at low ionic strength the complex formation is enthalpically favourable, but it becomes entropically driven when the salt concentration is increased. This may be explained considering the following reaction ... 

As with any other chemical species, solvated ions also have enthalpies and free energies of formation, and entropies. From equation 8.23, we can see that... 

Data for species in the gas phase at 1 bar have been summarized in Tables 1 to 5. Standard state enthalpies and free energies of formation, and entropies have been given at 298 K. In deriving reliable A,7/298 values from A, //(/ results corrections have been made on the basis of data in the literature. Values of A,G298 ... 

When thermodynamic parameters have not been measured for a sequence, they can often be predicted from the tables of parameters. Enthalpy, entropy, and free energy changes at 37 for helix formation can be calculated directly from the tables by adding the appropriate parameters. Free energy changes at other temperatures are calculated from ... 

Entropies of aqueous ions can be determined directly by measuring the enthalpy of solution of the metal to form the aquo ion and the free energy of solution of a salt of the ion. Upon correction to standard state, these data yield standard enthalpy and free energy of formation of the ion, from which its standard entropy... 

A general prerequisite for the existence of a stable interface between two phases is that the free energy of formation of the interface be positive were it negative or zero, fluctuations would lead to complete dispersion of one phase in another. As implied, thermodynamics constitutes an important discipline within the general subject. It is one in which surface area joins the usual extensive quantities of mass and volume and in which surface tension and surface composition join the usual intensive quantities of pressure, temperature, and bulk composition. The thermodynamic functions of free energy, enthalpy and entropy can be defined for an interface as well as for a bulk portion of matter. Chapters II and ni are based on a rich history of thermodynamic studies of the liquid interface. The phase behavior of liquid films enters in Chapter IV, and the electrical potential and charge are added as thermodynamic variables in Chapter V. 

Sodium Chlorite. The standard enthalpy, Gibbs free energy of formation, and standard entropy for aqueous chlorite ions ate AH° = —66.5 kJ/mol ( — 15.9 kcal/mol), AG = 17.2 kJ/mol (4.1 kcal/mol), and S° = 0.1883 kJ/(molK) (0.045 kcal/(molK)), respectively (107). The thermal decomposition products of NaClO, in the 175—200°C temperature range ate sodium chlorate and sodium chloride (102,109) ... 

Table 9.1 Standard heat capacities, entropies, enthalpies of formation, and Gibbs free energies of formation at T = 298.15 K. ...

Standard Gibbs free energies of formation can be determined in various ways. One straightforward way is to combine standard enthalpy and entropy data from tables such as Tables 6.5 and 7.3. A list of values for several common substances is given in Table 7.7, and a more extensive one appears in Appendix 2A. 

EXAMPLE 7.14 Calculating a standard Gibbs free energy of formation from enthalpy and entropy data... 

---