Air on Gases

In this chapter, 1 introduce you to gases at both the microscopic and macroscopic levels. 1 show you one of science s most successful theories the Kinetic Molecular Theory of Gases. 1 explain the macroscopic properties of gases and show you the important interrelationships among them. 

1 also show you how these relationships come into play in the calculations of chemical reactions involving gases. This chapter is a real gas  

The Kinetic Motecutar Theory Assuming Things about Gases 

A theory is useful to scientists if it describes the physical system they re examining and allows them to predict what will happen if they change some variable. The Kinetic Molecular Theory of Gases does just that. It has limitations 

Postulate 1 Gases are composed of tiny particles, either atoms or molecules. Unless you re discussing matter at really high temperatures, the particles referred to as gases tend to be relatively small. The more-massive particles clump together to form liquids or even solids, so gas particles are normally small with relatively low atomic and molecular weights. 

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Based on gases at atmospheric pressure, 38°C, containing water vapor, air, CO2, and mist, using negative polarity electrical discharge. Recalculated from data reported in reference 176. 

In addition to fulfilling the in-house requirements for quality control, state and local air monitoring networks which are collecting data for compliance purposes are required to have an external performance audit on an annual basis. Under this program, an independent organization supplies externally calibrated sources of air pollutant gases to be measured by the instrumentation undergoing audit. An audit report summarizes the performance of the instruments. If necessary, further action must be taken to eliminate any major discrepancies between the internal and external calibration results. 

The concentration of indoor pollutants is a function of removal processes such as dilution, filtration, and destruction. Dilution is a function of the air exchange rate and the ambient air quality. Gases and particulate matter may also be removed from indoor air by deposition on surfaces. Filtration systems are part of many ventilahon systems. As air is circulated by the air-conditioning system it passes through a filter which can remove some of the particulate matter. The removal efficiency depends on particle size. In addition, some reactive gases like NOj and SOj are readily adsorbed on interior surfaces of a building or home. 

This type of filling can create a pocket on the thin side and compresses cavity air and gases to such a point that the rising temperature caused by compression results in the material to be charred while the pocket is filling up. 

This equation defines the flow coefficient, Cv. Here, SG is the fluid specific gravity (relative to water), pw is the density of water, and hv is the head loss across the valve. The last form of Eq. (10-29) applies only for units of Q in gpm and hv in ft. Although Eq. (10-29) is similar to the flow equation for flow meters, the flow coefficient Cv is not dimensionless, as are the flow meter discharge coefficient and the loss coefficient (Af), but has dimensions of [L3][L/M]1/2. The value of Cv is thus different for each valve and also varies with the valve opening (or stem travel) for a given valve. Values for the valve Cv are determined by the manufacturer from measurements on each valve type. Because they are not dimensionless, the values will depend upon the specific units used for the quantities in Eq. (10-29). More specifically, the normal engineering (inconsistent) units of Cv are gpm/ (psi)1/2. [If the fluid density were included in Eq. (10-29) instead of SG, the dimensions of Cv would be L2, which follows from the inclusion of the effective valve flow area in the definition of Cv]. The reference fluid for the density is water for liquids and air for gases. 

Polishing is also an important application area of the surface chemistry of solids. The surface layer produced after polishing may or may not remain stable after exposure to its surroundings (air, other gases, oxidation). The polishing industry is much dependent on surface molecular behavior. 

Since Priestley found that some gases can he collected over water while others require mercury (41), he concluded that there must be different kinds of airs. On August 1, 1774, he heated mercuric oxide... 

Boyle, like many scholars of his day, studied and published in a number of areas including theology, philosophy, science, and political thought. In the area of chemistry, Boyle, in the tradition of van Helmont, studied gases. Aided by his assistant Robert Hooke, Boyle used a vacuum pump to conduct experiments in which he discovered air was necessary for life, sound does not travel in a vacuum, and that the volume of a gas is inversely proportional to pressure. This last discovery is one of the basic gas laws, and today is known as Boyle s Law (see Chapter 9). Boyle applied his work on gases to a study of the atmosphere and determined the density of air, and how atmospheric pressure changes with elevation. 

Apparatus used by Priestley for investigations on gases. The tub is Priestley s pneumatic trough. From Experiments on Different Kinds of Air. Image courtesy of School of Chemical Sciences, University of Illinois at Urbana-Champaign. 

Conceptually, the most important point here is the clear distinction Rouelle made between the chemical and physical aspects of behavior. Historically, the most important point was the preparation this view made for the return of air, or gases, to chemical attention. As we shall see in Chapter Nine, the focused attention on air made possible the extension of the phlo-dgistic doctrine to pneumatic chemistry, to the increased benefit of both. 

Dalton, J., Experimental essays on the constitution of mixed gases on the force of steam or vapor from waters and other liquids, both in a Torricellian vacuum and in air on evaporation and on the expansion of gases by heart , Mem. Proc. Manchester Lit. Phil. Soc., 5, 535-602 (1802). 

The influence of atmospheric air on the properties of mineral materials manufactured in thermal processes is generally known. An example of the nature of this phenomenon as regards hardness, is a series of Vickers hardness tests of a material made of sintered corundum modified with 0.6% MgO sintered at 1950-2050 K in various environments. The sintering process is accelerated in the presence of hydrogen and is slowest in air thus allowing a material with optimum parameters to be obtained at a significantly lower temperature. The results, specified in Table 6.2.4, show the gases used as... 

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