Physical properties of gases

The most commonly measured physical property of a gas is liie pressure. Combined with the volume of the container, the pressure gives the number of moles of the gas combined with the vapor density, it gives the molecular weight of the gas. Besides the pressure, the other properties of major importance are the vapor density and the heat capacity. These three subjects will be considered here. 

Pressure-measuring devices may be divided into two groups those which measure the pressure directly and can be calibrated without reference to another intrument and those which involve some other physical measurement which will be related to the pressure. Of the former type, the barometer, manometer, and McLeod gauge are the most common. 

The barometer is an 800-mm or longer tube which is sealed at the upper end, filled with mercury (Fig. 3-la), and inserted into a pool of mercury. If it has been filled in such a way as to avoid having air trapped in the upper end (e.g., by distilling in the mercury under a good vacuum), the height of the mercury column above the pool gives the atmospheric pressure. A temperature correction is usually applied, so that the readings correspond to that of a mercury column at 0°C. The open-end manometer (Fig. 3-1/ ) is closely related to the 

The closed-end manometer (Figs. 1-21 and 3-lc) is essentially a barometer, the lower end of which may be attached to the system whose pressure reading is desired. The difference in height between the mercury columns gives the system pressure, provided that both 

Manometers of this type may ordinarily be read to 0.25 mm if a well-designed scale is used and are satisfactory for pressures greater than 10 mm. For lower pressures or higher accuracy, the sensitivity may be increased by one of two methods. First, the manometer may be tilted so that the mercury will rise a considerable distance along the length of the tube per unit of vertical rise. Second, the manometer  

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The classical kinetic theoty of gases treats a system of non-interacting particles, but in real gases there is a short-range interaction which has an effect on the physical properties of gases. The most simple description of this interaction uses the Lennard-Jones potential which postulates a central force between molecules, giving an energy of interaction as a function of the inter-nuclear distance, r. 

Chapman and Enskog (see Chapman and Cowling, 1951) made a semi-empirical study of tire physical properties of gases using the Lennard-Jones... 

Table C-1 Physical Properties of Gases (Approximate Values at 68°F and 14.8 psia)... 

Table 6.2 Comparison of typical physical properties of gases, SCFs and liquids [3]...

Anesthesiologists must have an intimate knowledge of the chemical and physical properties of gases. Many anesthetics are inhaled and are delivered to the bloodstream by diffusion. The speed at which diffusion occurs between the lungs, the blood, and other tissues of the body depends on a constant called the partition coefficient This constant is a ratio that describes the equilibrium concentrations of a solute that is dissolved in two separate phases. The solute becomes separated (partitioned) between the two solvents in such a way that its concentration in one is directly proportional to its concentration in the other. 

The ideal gas law has been used in many examples in earlier chapters, and some of the important physical properties of gases (the one-dimensional velocity distribution, average speed, and diffusion) were presented in Chapter 4. This chapter puts all of these results into a more comprehensive framework. For example, in Section 7.3 we work out how the diffusion constant scales with pressure and temperature, and we explore corrections to the ideal gas law. 

Table 3.3. Physical Properties of Gases, Supercritical Fluids, and Liquids...

Table 3.3 presents the approximate physical properties of gases, supercritical fluids, and liquids. It shows that the densities of supercritical fluids are close to that of a liquid, whereas their viscosities are gaslike. The diffusion coefficients are in between. Due to these unique properties, supercritical fluids have good solvating power (like liquid), high diffusivity (better than liquid), low viscosity, and minimal surface tension (like gas). With rapid mass transfer in the supercritical phase and with better ability to penetrate the pores in a matrix, extraction is fast in SFE, along with high extraction efficiency. 

The physical properties of gases do not depend on the composition of the gas. Pressure is defined as force per nnit area. The pressure of a gas may be measured with a simple barometer, and one of the usual units used for pressure is related to that apparatus. A torr is the pressure required to hold one millimeter of mercury vertically in the barometer, and a standard atmosphere is the pressure required to hold 760 mm Hg vertically in the barometer (Section 12.1). 

Physical Properties of Gases, Kimball. Houghton, Mifflin, Co. 238 pp. 1.25. 

You will use the kinetic-molecular theory to explain the physical properties of gases, liquids, and solids. 

THIS PROGRAM CALCULATES THE PHYSICAL PROPERTIES OF GASES AT A TEMPERATURE RANGE FROM 300K TO 1500K FOR SOME GASES AND 26.80C TO 1026.8oC FOR OTHERS. 

The gas laws we will study in this chapter are the product of countless experiments on the physical properties of gases that were carried out over several centuries. Each of these generalizations regarding the macroscopic behavior of gaseous substances represents a milestone in the history of science. Together they have played a major role in the development of many ideas in chemistry. 

In the nineteenth centnry, a number of physicists, notably Lndwig Boltzmann and James Clerk Maxwell, fonnd that the physical properties of gases can be explained in terms of the motion of individual molecules. This molecular movement is a form of energy, which we define as the capacity to do work or to prodnce change. In mechanics, work is defined as force times distance. Since energy can be measured as work, we can write... 

Table 6.1 I A Comparison of Physical Properties of Gases, Liquids, and Solids ...

Curiously enough, a method of solving this problem had already been provided by the Italian pliysicist, Av< adro, in 1811, who from a study of the general physical properties of gases, notably their universal obedience to Boyle s Law, came to the conclusion that equal volumes of all gases at the same temperature and pressure contain equal numbers... 

The purpose of the kinetic theory of gases is to explain the physical properties of gases from the hypothesis that a gas consists of a great number of molecules in rapid motion. The following illustrations are based, in the first instance, on a memoir by R. Clausius (Phil. Mag., [4], 17, 81, 1859). For further developments, O. E. Meyer s The Kinetic Theory of Gases, London, 1899, may be consulted. 

The first study of the physical properties of gases was done by Robert Boyle (1627-1691) some 300 years ago. He studied the variation in volume of a gas with changes in pressure. He found that the product of the pressure and volume was a constant at constant temperature. In Fig. 5-2, the pressure of a gas confined in a cylinder with a moveable piston is plotted versus its volume at three different... 

Samuilov, E.V (1973), Thermo-Physical Properties of Gases, Nauka (Science), Moscow, p. 153. 

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