Gases gaseous solutions

Oil expulsion from good oil-prone source rocks is very efficient, whereas oil expulsion from leaner source rocks is relatively inefficient. Probably, most of the oil generated in leaner oil-prone source rocks will remain in the source rock and be cracked to gas at higher temperatures and expelled as gas condensate followed by dry gas. Gaseous solution cem be an effective migration mechanism for oil generated from mature type III kerogen. The expulsion of gas is very efficient. 

All gas mixtures are homogeneous hence all gas mixtures are solutions. Air is an example. There is only one phase—the gas phase—and all the molecules, regardless of the source, behave as gas molecules. The molecules themselves may have come from gaseous substances, liquid substances, or solid substances. Whatever the source of the constituents, this gaseous solution, air, is a single, homogeneous phase. As with other solutions, the constituents of air are separated by phase changes. 

The first term inside the brackets evidently is the energy of a solute molecule J in the perfect gas (cf. Eq. 10) hence we have for the energy of formation of the clathrate from and the gaseous solute at constant volume per molecule of Q... 

For the gas hydrates it is not possible to make an entirely unambiguous comparison of the observed heat of hydrate formation from ice (or water) and the gaseous solute with the calculated energy of binding of the solute in the ft lattice, because AH = Hfi—Ha is not known. If one assumes AH = 0, it is found that the hydrates of krypton, xenon, methane, and ethane have heats of formation which agree within the experimental error with the energies calculated from Eq. 39 for details the reader is referred to ref. 30. 

In the previous sections, we emphasized that at constant temperature, the liquid-phase activity coefficient is a function of both pressure and composition. Therefore, any thermodynamic treatment of gas solubility in liquids must consider the question of how the activity coefficient of the gaseous solute in the liquid phase varies with pressure and with composition under isothermal conditions. 

Gaseous solutions are easy to prepare and easy to describe. The atoms or molecules of a gas move about freely. When additional gases are added to a gaseous solvent, each component behaves independently of the others. Unless a chemical reaction occurs, the ideal gas equation and Dalton s law of partial pressures describe the behavior of gaseous solutions at and below atmospheric pressure (see Chapter 5). 

As mentioned above, gases in solution are often measured in partial pressures. Recall that Dalton s Law of Partial Pressures states that the total pressure is the sum of the pressures partially exerted by all of the component, noninteracting gases. For one gaseous component in equilibrium with the same component dissolved in a liquid, the partial pressure of that gas in solution is the pressure that gas would exert in the atmosphere. It is symbolized by either p or P followed by the specific gas (eg, either or pO ). For example, typical blood P02 levels range between 75 and 100 torr (or, 10.0 to 13.3 kPa since the pascal (Pa) is an SI unit). 

Just as water bodies such as rivers, lakes, and the ocean can be considered enormous aqueous solutions, the atmosphere is a gigantic gaseous solution. The atmosphere is composed primarily of nitrogen, 78%, and oxygen, 21%. The third most abundant gas in the atmosphere is argon, which makes up about 0.9%. The remaining 0.1% consists of... 

Compressed Gas (Non-Iiquefied) Under U.S. Department of Transportation regulations (refer to 49 CFR 173.300), a non-liquefied compressed gas is defined as a gas other than gas in solution which under the charged pressure is entirely gaseous at a temperature of 70 °F. 

So far we have considered only pure, one-component systems. When a solute dissolves in such a system, it produces a solution—a homogeneous mixture of two or more components—which can be solid, liquid, or gas. The solute affects the physical properties of the solvent. Solid solutions of solutes in metalloid and nonmetal solvents, such as silicon doped with a tiny amount of phosphorus as solute, exhibit electrical properties that make them the primary materials of the electronics industry (Section 3.13). When we spread salt on icy sidewalks, we are creating a mixture of salt and water that lowers the freezing point of water. If that temperature is lower than the ambient temperature, the ice melts. Gaseous solutions—which are more commonly regarded simply as mixtures—are used... 

When the only effects that have to be taken into account are those of cavity formation in the solvent and the dispersion interactions, i.e., when both the solvent and the solute are non-polar, then Hildebrand s solubility parameter concept (Hildebrand and Scott 1950) provides good estimates of the solubility. The mole fraction of a gaseous solute, x2, in a solution in equilibrium at a partial pressure p2 of this gas, can be estimated from the following expression ... 

Pressure has a dramatic affect on the solubility of gaseous solutes in liquid solvents. As pressure increases, the solubility of a gaseous solute in a liquid solvent increases. You have no doubt observed this phenomenon when opening a carbonated beverage. Have you noticed that when you open a bottle of champagne (or soda pop, or beer, or club soda), small bubbles of carbon dioxide gas start to form That pop you hear when removing the cork is caused by the escape of excess carbon dioxide gas from the bottle. When the gas escapes, the pressure in the container decreases. With less pressure, the solubility of the carbon dioxide dissolved in the wine decreases. As the carbon dioxide comes out of the solution, it forms those tiny (wonderful) little bubbles. Since solids and liquids are not very compressible, at least not compared to gases, pressure has very little effect on the solubility of solid and liquid solutes. 

The solubility of solid and liquid solutes in liquid solvents generally increases with increasing temperature. There are a few exceptions to this rule, but not many. This is why there are a few medications that are stored at room temperature. For example, a concentrated mannitol solution will crystallize if stored at low temperatures. Warming the solution will cause the crystallized solid to redissolve. Temperature has the opposite effect on the solubility of gaseous solutes in liquid solvents. As the temperature increases, the vapor pressure of the gaseous solutes increases to the point that they can escape the solvent into the gas phase. 

In gas chromatography (GC), a gaseous solute (or the vapour from a volatile liquid) is carried by the gaseous mobile phase. In gas-liquid partition chromatography, the stationary phase is a non-volatile liquid coated on the inside of the column or on a fine support. In gas-solid adsorption chromatography, solid particles that adsorb the solute act as the stationary phase. 

Similarly a gaseous solution may be maintained supersaturated in such conditions of temperature and pressure that, according to thermod3mamics, the gas should be liberated... 

The supersaturation of gaseous solutions, which ceases by the introduction of a bubble of gas ... 

PGSS = particles from gas-saturated solution (gaseous CO2 is dissolved in a melted drug and the gas-saturated solution is expanded). 

A solution may exist as a gas, liquid, or solid depending on the state of its solvent, as shown in Figure 15-1 and Table 15-1 on the next page. Air is a gaseous solution, and its solvent is nitrogen gas braces may be made of niti-nol, a solid solution of titanium in nickel. Most solutions, however, are liquids. You learned in Chapter 10 that reactions can take place in aqueous soluhons, that is, soluhons in which reactants and products are mixed in water. In fact, water is the most common solvent among liquid solutions. 

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