Values of the Gas Constant in Different Unit Systems

At integrating (305) for the conditions of a flow system (93, 98), it proved to be convenient to introduce a constant k proportional to k. The value of k was also calculated from data obtained in circulation flow systems (4, 96, 99-103). If the volume of ammonia reduced to 0°C and 1 atm, formed in unit volume of catalyst bed per hour, is accepted as a measure of reaction rate, then k = (4/3)3 1 m)k (101). The constancy of k at different times of contact of the gas mixture with the catalyst and different N2/H2 ratios in the gas mixture can serve as a criterion of applicability of (305). Such constancy was obtained for an iron catalyst of a commercial type promoted with A1203 and K20 at m = 0.5 (93) from our own measurements at atmospheric pressure in a flow system and literature data on ammonia synthesis at elevated pressures up to 100 atm. A more thorough test of applicability of (305) to the reaction on a commercial catalyst at high pressures was done by means of circulation flow method (99), it confirmed (305) with m = 0.5 for pressures up to 300 atm. Similar results were obtained in a large number of investigations by different authors in the USSR and abroad. These authors, however, have obtained for some promoted iron catalysts m values differing from 0.5. Thus, Nielsen et al. (104) have found that m 0.7. 

Substituting in equation 11 the known experimental parameters for phenol dissociation (AG, = 13.8 kcalmol" calculated from the ground-state equilibrium constant, pX, = 10.0), AGt((PhO ) — (PhOH)) of the phenolate/phenol system is about —76 kcalmoH, which is about 10% less than the accepted value for the electrostatic solvation energy of the chloride anion in water, AGe(Cr) = —85 kcalmol". These simple considerations imply that the AGt((PhO ) — (PhOH)) contribution to the overall free energy of solvation is largely electrostatic, and that relatively small differences in the gas-phase proton affinity of the base and in specific solvent-solute interactions of the photoacid and the base determine the relatively narrow (in free-energy units) acidity scale in aqueous solution. It... 

Note that Henry s constant is expressed in various other units, for example, in conjunction with kinetic equations for gas-liquid systems (Section 4.4). If the gas phase concentration is denoted in pressure units (Pa) and the liquid phase concentration in molarity (mol m ), a different unit for Henry s constant is obtained (Ha,c = Pa/ca, Pam mol ). If both the liquid and the gas phase concentrations are expressed as molar fractions, a dimensionless value is obtained for Henry s constant. Therefore, be careful in noting the correct units obtained from the literature. In addition, note that in older literature an absorption coefficient is frequently used, for example, the Bunsen absorption coefficient bu (in ni m bar ) defined as the volume of gas (at 1.013 bar and 0°C) absorbed by one volume of liquid at a certain pressure, for example, 1 bar. Thus bu is inversely proportional to and equivalent to the term /Omoi,iiq 0.0224 m morVWx-... 

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