Enthalpy of formation table

These gases have lower thermal stabilities than hydrogen sulphide as expected from their enthalpies of formation Table 10.2) and they are consequently more powerful reducing agents than hydrogen sulphide. 

The methods summarized by Eqs. 8 and 9 have both been applied to halocarbenes. The proton affinities obtained by ICR bracketing125 (Table 6) are consistently lower than those derived from enthalpies of formation (Table 7). The case of dichlorocarbene, with a difference in AH of 15 kcal/mol), is particularly disturbing and has been analysed in some detail.134 Notably, the PA of CCl2 from an earlier bracketing experiment126 was closer to the enthalpy-derived PA. The discrepant results from similar experiments125126 indicate that HCClJ is not a good substrate for proton transfer studies. 

Enthalpy of Formation. Tables of enthalpies of reaction generally list the enthalpies of formation of various compounds in their standard states from the elements in their standard states at the specified temperature. Thus, if the standard molar enthalpy of formation, Af//, of CO2 at 25°C is given as —393.509 kJ mol , the following equation is implied ... 

Consulting the standard enthalpies of formation (Table l4-3), what is the enthalpy change, AH, for this reaction ... 

Flowing ammonia has been applied to the synthesis of the nitrides of iron, cobalt, and nickel compounds with very low enthalpies of formation (Table 2). Again, isothermal conditions were employed. Ammonia is preferable over the use of molecular nitrogen to nitride... 

The enthalpy change for this reaction can be called the enthalpy of formation of water, A//y (H20). Table 14.6 shows standard enthalpies of formation. Table 14.7 is a separate table for unbranched hydrocarbons. 

Trends in enthalpies of formation (Table 4) are not as regular as those of lattice energy. For fluorides, lattice energies dominate A//f therefore the smallest cation gives the most stable fluoride. For the other hahdes, the ease of production... 

If we compare the estimated enthalpies of formation (Table 1) for (Z,Z)-mucon-aldehyde (14a) and rroRj-cyclobutene-l,2-dicarboxaldehyde (see Eq. 4), we find that the isomerization to 22b is endothermic by 16.9 kcal/mol, about 11 kcal/mol more endothermic than isomerization to the 2f/-pyran 19. This plausibly explains the rapid Z,Z to Z,E isomerization coupled with very slow Z, to , isomerization in the absence of nucleophiles. Thus, the first step could be unimolecular thermal rearrangement, while the second step under metabolic conditions could be the reversible Michael addition-isomerization. Of course, both steps could result from attack by nucleophiles either in the medium or on biological macromolecules. 

The synthesis and properties of several high-nitrogen materials with 3-amino-6-nitroamino-tetrazine (ANAT) as the anion are reported (Scheme 23). These salts (99, 100, 103a,b) provide a new and easy approach to highly energetic salts. All these salts are relatively dense (> 1.55 g/cm ) and exhibit good thermal stability T > 148 C). The calculated detonation velocities and detonation pressures are comparable to those of explosives such as Tetryl, PETN, TATB, and RDX. A combination of theoretical and empirical calculations shows that all these salts have high molar enthalpies of formation (Table 9) [99]. 

Calculate the heat of vaporization, A.H°ap, of water, using standard enthalpies of formation (Table 6.2). 

Table B-1 SI Measurement Table B-2 Unit Symbols Table B-3 Symbols Table B-4 Physical Constants Table B-5 Enthalpy of Combustion Table B-6 The Elements Symbols, Atomic Numbers, and Atomic Masses Table B-7 Common Ions Table B-8 Water-Vapor Pressure Table B-9 Densities of Gases at STP Table B-10 Density of Water Table B-11 Solubilities of Gases in Water Table B-12 Solubility Chart Table B-13 Solubility of Compounds Table B-14 Enthalpy of Formation Table B-15 Properties of Common Elements...

Standard Enthalpies of Formation—By arbitrarily assigning an enthalpy of zero to the reference forms of the elements in their standard states, the enthalpy change in the formation of a compound from its elements becomes a standard enthalpy of formation (AfH°). Using tabulated standard enthalpies of formation (Table 7.2), it is possible to calculate standard enthalpies of reactions without having to perform additional experiments (equation 7.22). 

Table 5.1 gives a sample calculation of the NHVj for toluene, starting from the molar enthalpies of formation of the reactants and products and the enthalpies of changes in state as the case requires. 

The enthalpy (strictly, the enthalpy change) for a reaction can readily be calculated from enthalpies of formation AHf which can often be obtained from tables of data. 

Data on proton affiri itics (gas ph asc) of m any differen t com poti u ds (see Table 2) deni on strate Lh e h igh level of accuracy possible in determ in in g energies of related species. In th is report by Dew-ar and Dieter , the enthalpy of formation of II is the experimental value (367.2 kcal/moll. The calculated value for H is unreliable. 

Arylthiazoles derivatives are good subjects for the study of these transfers. Thus the absorption wavelengths and the enthalpies of formation of a series of charge-transfer complexes of the type arylthiazole-TCNE, have been determined (147). The results are given in Table IIM3. 

This table gives the first ionization potential in MJ mol and in electron volts. Also listed is the enthalpy of formation of the ion at 25°C (298 K). 

Several portions of Section 4, Properties of Atoms, Radicals, and Bonds, have been significantly enlarged. For example, the entries under Ionization Energy of Molecular and Radical Species now number 740 and have an additional column with the enthalpy of formation of the ions. Likewise, the table on Electron Affinities of the Elements, Molecules, and Radicals now contains about 225 entries. The Table of Nuclides has material on additional radionuclides, their radiations, and the neutron capture cross sections. 

Physical properties of the acid and its anhydride are summarized in Table 1. Other references for more data on specific physical properties of succinic acid are as follows solubiUty in water at 278.15—338.15 K (12) water-enhanced solubiUty in organic solvents (13) dissociation constants in water—acetone (10 vol %) at 30—60°C (14), water—methanol mixtures (10—50 vol %) at 25°C (15,16), water—dioxane mixtures (10—50 vol %) at 25°C (15), and water—dioxane—methanol mixtures at 25°C (17) nucleation and crystal growth (18—20) calculation of the enthalpy of formation using semiempitical methods (21) enthalpy of solution (22,23) and enthalpy of dilution (23). For succinic anhydride, the enthalpies of combustion and sublimation have been reported (24). 

Values for the free energy and enthalpy of formation, entropy, and ideal gas heat capacity of carbon monoxide as a function of temperature are listed in Table 2 (1). Thermodynamic properties have been reported from 70—300 K at pressures from 0.1—30 MPa (1—300 atm) (8,9) and from 0.1—120 MPa (1—1200 atm) (10). 

Table 1.5. Standard Enthalpies of Formation of Some Hydrocarbons (kcal/mol) ...

Theoretical studies of the relative stabilities of tautomers 14a and 14b were carried out mostly at the semiempirical level. AMI and PM3 calculations [98JST(T)249] of the relative stabilities carried out for a series of 4(5)-substituted imidazoles 14 (R = H, R = H, CH3, OH, F, NO2, Ph) are mostly in accord with the conclusion based on the Charton s equation. From the comparison of the electronic spectra of 4(5)-phenylimidazole 14 (R2 = Ph, R = R3 = H) and 2,4(5)-diphenylimidazole 14 (R = R = Ph, R = H) in ethanol with those calculated by using ir-electron PPP method for each of the tautomeric forms, it follows that calculations for type 14a tautomers match the experimentally observed spectra better (86ZC378). The AMI calculations [92JCS(P1)2779] of enthalpies of formation of 4(5)-aminoimidazole 14 (R = NH2, R = R = H) and 4(5)-nitroimidazole 14 (R = NO2, R = R = H) point to tautomers 14a and 14b respectively as being energetically preferred in the gas phase. Both predictions are in disagreement with expectations based on Charton s equation and the data related to basicity measurements (Table III). These inconsistencies may be... 

Table 2 Calculated and experimental values for the equilibrium volumes, bulk moduli and enthalpies of formation.

Table 2 gives our calculated results for the equilibrium volume Vq, bulk modulus Bq, and enthalpy of formation AH. Theoretical results refer to T=0, uncorrected for zero point motion, whereas experimental values refer to room temperature. Note that the extensive quantities AH and Vq arc reported per atom in the present paper, i.e., divided by the total number of atoms. As well known the LDA underestimates the volume. Comparing the bulk modulus for T3 and D8s we see that the addition of Si to pure Ti has a large (26 %) effect on the bulk modulus, indicating that p electrons of Si have a strong effect on the bonding in this system. 

Enthalpies of formation for a variety of compounds are listed in Table 8.3. Notice that, with a few exceptions, enthalpies of formation are negative quantities. This means that the formation of a compound from the elements is ordinarily exothermic. Conversely, when a compound decomposes to the elements, heat usually must be absorbed. 

You will note from Table 8.3 that there are no entries for elemental species such as Br2(l) and O2(g). This is a consequence of the way in which enthalpies of formation are defined. In effect, the enthalpy of formation of an element in its stable state at 25°C and 1 atm is taken to be zero. That is,... 

The standard enthalpies of formation of ions in aqueous solution listed at the bottom of Table 8.3 are relative values, established by taking... 

Strictly speaking, AH° calculated from enthalpies of formation listed in Table 8.3 represents the enthalpy change at 25°C and 1 atm. Actually, AH is independent of pressure and varies relatively little with temperature, changing by perhaps 1 to 10 kj per 100°C. 

Table 4.3 summarizes values taken from the JANAF tables for the Gibbs free energy functions and standard enthalpies of formation for a few common substances. The JANAF tables provide a more complete tabulation. 

We will see in a later chapter how to calculate A,H° from enthalpies of formation, from which ArG° can be calculated using Table 4.3 and equations (4.34) or (4.36). 

Extensive tabulations of standard enthalpies of formation and related thermodynamic data can be found in the literature.5 Table 9.1 summarizes selected values from these sources. 

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

The group contributions are given in Table 6. The group values were used to predict the enthalpy of formation of every compound in Tables 1-5 (except for those containing nitrogen). The estimated values were then compared to the experimental values. The agreement was usually to within about 10 kJ mol f The worst cases were for butyl methyl sulfone, t-butyl methyl sulfone and l-methyl-4-(l-methylethenylsulfonyl)benzene, for which the deviations were 12.4, 14.0 and 12.3 kJ mol-1, respectively. The average deviation was 4.4kJ mol-1. 

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