Constants, Units, Tables

The value of R changes if we express the ideal-gas equation (Equation (1.13)) with different units. Table 2.3 gives values of R in various other units. We must note an important philosophical truth here the value of the gas constant is truly constant, but the actual numerical value we cite will depend on the units with which we express it. We met a similar argument before on p. 19, when we saw how a standard prefix (such as deca, milli or mega) will change the appearance of a number, so V = 1 dm3 = 103 cm3. In reality, the number remains unaltered. 

Rate constant units for zero to third order reactions are summarised in the table on the left. 

Finally, table A1.5 lists the principal physical constants, and table A1.6 presents some energy equivalents of atom units. 

The basic thermophysical properties of selected gases at 1 atm is shown in Table 1.6. Gas constant units... 

Table 6.4. Compilation of the H-abstraction rate constants (unit dm3 mol1 s ) of some radicals from alcohols in aqueous solution at room temperature...

Table 10.3. Compilation of rate constants (unit dm3 mol nudeobases and related compounds 1 s ) of oxidizing radicals with...

Table 12.17. Rate constants (unit dm3 mol 1 s 1) of the reaction of Hoechst 3342 with some nucleotide-derived radicals. (Adhikary et al. 1997b)...

Table 12.20. Second-order rate constants (unit dm3 mol 1 s ) for fixation by 02 and chemical repair by GSH of SSB and DSB free-radical precursors. (Prise et al. 1999) ...

The data obtained in these equilibrium studies have been treated quantitatively by Carmichael and Heffel (53) and by Brown and Slusarczuk (33), who evaluated the equilibrium data in terms of cyclization constants. The latter are identical with ring-chain constants of the type of Eq. (29) where the concentrations are expressed in mole fractions of building units. Table XI... 

Figure 1. Computer curves for loss of folding endurance (washed Kraft, MD) with rate constants of Table IV. The curves pass through the data for (D) 70°C, (O) 80°C, and (+) 90°C. The data for the curve at 70°C has been displaced upward by 300 units for clarity.

Coke selectivity directly influences the rate of catalyst deactivation as seen by comparing coke selectivities in Tables VI and VII with observed rate constants in Table V. Our data indicate calcined AFS zeolites show higher coke selectivities than USY zeolites when compared at similar unit cell sizes. This result suggests that distribution of framework acid sites(as reflected by the distribution of framework silicon) has a strong impact on coke selectivity. In addition, coke selectivity has been shown to correlate with the density of strong acid sites in the framework(20). Our data confirm this and show that steaming decreases the density of such sites which, in turn, leads to decreased coke selectivities. 

The solvent term [H20] varies by a negligible amount in such reactions and is incorporated in the constants Kt and Kh. If the concentrations are expressed in mol dm Kt and Kh have the same units. Table 3.3 lists pKt values for some typical compounds. The behaviour of the conjugate base may be represented in line with equation(3.15). 

Note that tabulating data is very helpful when two or more variables are being considered. The units are usually included in the column headings in such a table. The data in the table show that the product of the volume (V) and the pressure (P) is a constant. The table may be expanded to show this relationship ... 

The equSibrium constants K (Table 2) were calculated from the change in absorption at 420 nm in electronic spectra The very low value of K in the homopolymer of 4-vinyl-jqrridine (PVP).is explained by steric hindrance near the coordinated cobaloximes through the neighbouring base. If the content of 4-vinylpyridine in the copolymer is lower than 20%, the coordinated cobaloxime was easily removed because coordination occurs mainly at the surface of the polymer domain. In unpolar benzene instead of DMF, however, the conformational change of polymer chain brings the vinyl-pyridine units more to the interior of the polymer domain. 

Values oiA,B, and C for several compounds are listed in Table B.4. Observe the units of p and T (mm Hg and °C for the constants in Table B.4) and the logarithm base (10 in the case of Equation 6.1-4 and Table B.4). Gathering parameters from multiple sources increases the need for care relative to the units used. 

Table 6 Calculated force constant (unite is mdyne/A)...

In Eq. (38) is shown an adaptation of Eq. (37) based on exciplex intermediacy which gives an overall quenching rate constant defined by Eq. (39). The numbers in the boxes besides each rate constant in Eq. (38) are appropriately chosen room temperature rate constants (units omitted) and activation energies in kcal mol-1. The value of 10101 mol-1 s-1 for kD is perfectly reasonable and the activation energy is taken from Table 3 (diffusion limit where a = AH1 + RT). 

The effect of pressure on calculated pH, activities of several aqueous species, and saturation states of selected minerals for the seawater are listed in Table 4. The calculated pH at higher temperatures and 500 bars pressure is 0.1 unit lower than that calculated for pressures along the vapor saturation curve at 1000 bars pressure, the pH is lower by --0.2 units (Table 4). At 500 bars pressure, the predicted saturation states of calcite are greater by -200 cal (ASI=0.15) at 25°C, and 1800 cal (ASI=0.75) at 250°C, compared to those calculated without considering the effect of pressure on the ionization constants (Figure 7). Similar, but numerically larger, differences are seen for the saturation state of anhydrite. 

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