Henry’s Law The concentration

In Region I the concentration of surfactant in the bulk solution is very low, and typically the solution obeys Henry s Law. The concentration of surfactant adsorbed on the surface of the solid is also very low. As shown in Figure 8, the adsorbed molecules are believed to "lie down," maximizing their contact with the solid. 

The solubility of carbon dioxide under conditions where it does not undergo significant reaction (such as acidic aqueous solutions) is governed by Henry s law the concentration of CO2 in solution is proportional to its partial pressure in the gas phase ( 3) ... 

The notation is explained in Fig. 1-16, and Dg and DL are the molecular diffusion coefficients for air and for seawater, respectively. The flux is maintained by the concentration differences across the molecular diffusion layers. The flux is directed from the ocean into the atmosphere when the concentration in seawater is greater than that at the interface the flux is directed from the atmosphere into the ocean when the concentration difference is negative. If the exchanging gas obeys Henry s law, the concentrations at the gas-liquid interface are connected by... 

From Henry s law, the concentration of any gas dissolved in a fluid is proportional to the partial pressure of that gas above the fluid. For 02, this is expressed as PO2. 

Henry s law The concentration (C) of a gas in solution is proportional to the partial pressure (p) of that gas in equilibrium with the solution, i.e. p = kC, where k is a proportionality constant. The relationship is similar in form to that for Raoult s law, which deals with ideal solutions. 

Henry s Law The concentration or solubiUty of a gas in a liquid at any given temperature is directly proportional to the partial pressure of the gas over the solution. 

According to Henry s law, the concentration of ethanol in the headspace of a blood sample in a closed vial is directly proportional to the concentration of ethanol in the blood solution when the system is in equilibrium. Thus the concentration of ethanol in the blood can be determined by measuring the peak area, or height, of a chromatographic peak resulting from a static headspace sample. The principles of Hemy s law are described in Chapter 11 of this book. 

Absorption, Dissociation, and Aqueous-Phase Chemical Reactions The diffusive penetration of gases or gas mixtures into a condensed phase (e g., droplet) is called absorption. In equilibrium, the absorbed gas is dissolved at a certain concentration inside the droplet and the equilibrium vapor pressure over the droplet surface is proportional to the concentration at the droplet surface (Henry s law). The concentration inside the droplet itself can be influenced by dissociation or chemical reactions (sulfur production by oxidation of dissolved SO2 to SOt ). If these processes represent a sink for the solute, the concentration inside the droplet and, consequently, the vapor pressure at the droplet surface is decreased (i.e., mass transfer is enhanced). Typical gases that dissolve into atmospheric water droplets are CO2, SO2, NH3, H2O2, and O3. 

The interrelationships of the various coefficients associated with fluid uptake (Section 23.4.2) mean that it should be possible to estimate a rate for one of the uptake phenomena from test data for another of them. Campion proposed using this approach to estimate permeation coefficient Q from solubility coefficient s. The form of a liquid absorption plot (Figure 23.6, Section 23.4.4.1) is such that s should be obtainable from it, and inspection showed that this link was via Henry s law with concentration corrected by the polymer density p. The following expression was derived for s ... 

Expressions for 9 SM and H2 can be derived and related to rate (k) and equilibrium constants (K). The SI and S2 site balances are 9SM +9a + S, = 1 and //2 + S2 = 1 respectively 9sx, S2 are empty sites). Based on Henry s law, the gas-phase hydrogen pressure and the liquid-phase hydrogen concentration may be used interchangeably. The rate expression can be written as follows ... 

To determine the amount of substance and the concentration of carbon monoxide in solution, we have to relate these quantities to the CO pressure. That can be done as described by using Henry s law. The only (important) difference is that now the CO pressure is too high to justify use of the ideal gas model. Hence, for the present case, equation 14.15 becomes [316]... 

According to Henry s law, the vapour pressure of a gas above its solution is directly proportional to the concentration c, or the mole fraction Xg of this gas in solution. It applies if the solutions are sufficiently ideal. 

Henry s law The partial pressure of a gas in equilibrium with gas dissolved in a solution is proportional to the concentration of dissolved gas P = Hdissolved gas]. The constant k is called the Henry s law constant. It is a function of the gas, the liquid, and the temperature, hertz. Hz Unit of frequency, s-1. heterogeneous Not uniform throughout. 

Thus, in the domain of validity of Henry s law, the equilibrium concentration is proportional to the relative hygrometry (at a given temperature). 

Air-water partitioning can be viewed as the determination of the solubility of a gas in water as a function of pressure, as first studied by William Flenry in 1803. A plot of concentration or solubility of a chemical in water expressed as mole fraction x, versus partial pressure of the chemical in the gaseous phase P, is usually linear at low partial pressures, at least for chemicals which are not subject to significant dissociation or association in either phase. This linearity is expressed as "Henry s Law." The slope of the P-x line is designated H, the Henry s law constant (HLC) which in modern SI units has dimensions of Pa/(mol fraction). For environmental purposes, it is more convenient to use concentration units in water Cw of mol/m3 yielding H with dimensions of Pa m3/mol. 

Oxygen dissolves in water according to Henry s law, The partial pressure of a gas in a liquid is equal to the partial pressure of the gas above the liquid. Therefore, the DO concentrations depend on the atmospheric pressure. They are also temperature-dependent as the solubility of gases decreases with increasing temperature. Another factor that decreases the solubility of oxygen in water is the dissolved salt content the more salts are dissolved, the less room for oxygen to dissolve. 

At sufficiently low concentrations on a homogeneous surface the equilibrium isotherm for physical adsorption will always approach linearity (Henry s law). The limiting slope of the isotherm [limp o(dq/dp)T] is referred to as the Henry constant K . It is evident that the Henry con-... 

This distribution law applies only to the distribution of a definite chemical species, as does Henry s law. The distribution constant is not a true thermodynamic equilibrium constant, since it involves concentrations rather than activities. Thus it may vary slightly with the concentration of the solute (particularly because of the relatively high concentration of I2 in the CCI4 phase) it is therefore advantageous to determine 1 at a number of concentrations. It can be determined directly by titration of both phases with standard thiosulfate solution when I2 is distributed between CCI4 and pure water. Once k is known, (I2) in an aqueous phase containing I3 can be obtained by means of a titration of the I2 in a CCI4 layer that has been equilibrated with this phase. The use of a distribution constant in this manner depends upon the assumption that its value is unaffected by the presence of ions in the aqueous phase. 

At very dilute concentration range and in cases where Raoult s Law is not obeyed, activity is found to be proportional to the mole fraction. As stated in Sec. 7.2, the system obeys Henry s Law. The proportionality constant is referred to as the Activity Coefficient (Yb), of the constituent in the particular system. 

As seen in 32f, the molarity of a very dilute solution is proportional to its mole fraction, and hence for such solutions the activity coefficient y., defined by Oz/c, represents the compliance with Henry s law. As in the preceding case, 7, and 7n are both unity at infinite dilution, and the values are approximately equal in dilute solutions. With increasing concentration, however, y and 7n differ, and althou the latter still indicates the adherence to Henry s law, the former, like 7m, does not. Thus, at high dilutions 7n, 7values approximating to unity, but at appreciable concenis ations the three coefficients differ the actual relationships between them will be considered in the next section. 

This is a more convenient form of Henry s law. The constant m, (or //,) has been determined experimentally for a large number of compounds and is usually valid at low concentrations. In word equation form, Henry s law states that the partial pressure of a solute in equilibrium in a solution is proportional to its mole fiaction. The law is exact in the limit, as the concentration approaches zero. 

The rate of mass transfer was given by equation T14. Mass transfer between gas phase and liquid phase (Eq. T16) was only considered in this study. Mass transfer rate (Eq. T15) between gas phase and liquid phase can be expressed in terms of the volumetric mass transfer coefficient and the concentration difference between gas-liquid interface phase and liquid phase. Where, kia (sec ) is the volumetric mass transfer coefficient and is the concentration of the yxth species at gas-liquid interface phase which can be defined by Henry s law. The fugacity of a very dilute species in a liquid phase is linearly proportional to its mole fraction at low mole fractions. 

Rudzinski (2004) compared the rates of the aqueous-phase reaction of isoprene with sulphate radicals against the rates of the gas- and the aqueous-phase reactions of isoprene with OH radicals, NO3 radicals and ozone. The rates were evaluated for 25 C, typical atmospheric concentrations of reactants (Herrmann et at, 2000), and a LWC of 10 and 10. The partitioning of reactants between phases was described using Henry s Law. The results, shown in part in Table 4, indicated that the aqueous-phase reaction of isoprene with sulphate radicals was competitive against other reactions only in the aqueous phase and at very high values of liquid water content (LWC =10 ). 

During absorption of low-solubility gases, mass transfer from a highly concentrated gas mixture to a very dilute liquid solution frequently takes place. In that case, although it is appropriate to use a k-type mass-transfer coefficient in the liquid phase, an F-type coefficient must be used in the gas phase. Since dilute liquid solutions usually obey Henry s law, the interfacial concentrations during absorption of low-solubility gases are related through... 

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