Densities of gases

The density, d, of a gas is its mass per unit volume, which is generally expressed in grams per liter as follows  

Because the volume of a gas depends on temperature and pressure, both should be given when stating the density of a gas. The volume of a solid or liquid is hardly affected by changes in pressure and is changed only slightly when the temperature is varied. Increasing the temperature from 0°C to 50°C will reduce the density of a gas by about 18% if the gas is allowed to expand, whereas a 50°C rise in the temperature of 

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According to Avogadro s law, equal volumes of all gases under similar conditions contain the same number of molecules. Consequently the weights of equal volumes or the densities of gases will represent the ratio of their molecular weights. If the densities are compared with hydrogen as the unit, the ratio... 

The density, d, of a gas, like that of any substance, is the mass of the sample divided by its volume, d = tn/V. Because the densities of gases are so low, they are usually expressed in grams per liter (g-L ). The density of air, for instance, is about 1.6 g-L-1 at SATP. Because the mass of the sample is equal to the amount in moles times the molar mass, m = nM, and n = PV/RT, it follows that... 

The molar concentrations and densities of gases increase as they are compressed but decrease as they are heated. The density of a gas depends on its molar mass. 

The low density of gases makes it more difficult to keep the bubbles dispersed. The bubbles will move to the low-pressure areas, that is, behind the impellers, in the trailing vortices close to the impeller, behind the baffles, and at the inner side after a bend. The bubbles will coalesce in these areas with high gas holdup. It is very difficult to design reactors without low-pressure regions where the low-density fluid will accumulate. One such reactor is the monolith reactor for multiphase flow [32, 33]. 

It is necessary to use the proper units when calculating the density of a substance. Densities of liquids and solids are usually expressed in terms of g/mL or g/cm3. Densities of gases are usually expressed in g/L. 

The density of a material is a function of temperature and pressure but its value at some standard condition (for example, 293.15 K or 298.15 K at either atmospheric pressure or at the vapor pressure of the compound) often is used to characterize a compound and to ascertain its purity. Accurate density measurements as a function of temperature are important for custody transfer of materials when the volume of the material transferred at a specific temperature is known but contracts specify the mass of material transferred. Engineering applications utilize the density of a substance widely, frequently for the efficient design and safe operation of chemical plants and equipment. The density and the vapor pressure are the most often-quoted properties of a substance, and the properties most often required for prediction of other properties of the substance. In this volume, we do not report the density of gases, but rather the densities of solids as a function of temperature at atmospheric pressure and the densities of liquids either at atmospheric pressure or along the saturation line up to the critical temperature. 

Sir William Ramsay (1904, chemistry discovery of the noble gases) Lord John W. Rayleigh (1904, physics argon and density of gases)... 

In contrast to viscosity, the density of both liquids and gases decreases with increasing temperature, and the density of gases is much more sensitive to temperature than that of liquids. If the density of a liquid and its vapor are... 

Explosions in solids and liquids can be even more violent than in gases because the energy content per mole is comparable, but the density of sohds and liquids is approximately 1000 times the density of gases at atmospheric pressure. 

Could be applied to deton of condensed expls. Here the coefficient /3 was included in the exponential term to secure constancy of the k with respect to density of gases, and in which T 4 dependence of the covolume... 

Once gases were recognized as important in chemical reactions, they were immediately handled in quantitative ways, most conveniently through the measurement of their volumes and densities. Henry Cavendish was apparently the first to measure the densities of gases, as he did with inflammable air (hydrogen) and fixed air (carbon dioxide) in 1766. 

The density of gases for temperatures above the critical temperature Tc and pressure of few atmospheres can be evaluated by the ideal gas law (Perry and Green, 1999) ... 

In scientific work, the densities of solids and liquids usually are expressed in grams per cubic centimeter or grams per milliliter, whereas the densities of gases usually are expressed in grams per liter. In engineering work, densities customarily are expressed in pounds per cubic foot. 

The density of gases can be determined experimentally in the same way as for liquids, but the values so obtained are not particularly reliable because the total weight of gas in a flask of a reasonable size for weighing is very small—quite likely less than 100 mg. Furthermore, a very special flask would have to be used that would be absolutely leakproof and capable either of being flushed out with the gas to be studied, or of being evacuated before filling. Moreover, provision would have to be made for measuring the pressure of the gas in the flask as well as its temperature. 

Data of densities of liquids are empirical in nature, but the effects of temperature, pressure, and composition can be estimated suitable methods are described by Reid et al. (Properties of Gases and Liquids, McGraw Hill, New York, 1977), the API Refining Data Book (American Petroleum Institute, Washington, DC, 1983), and the AIChE Data Prediction Manual (1984-date). The densities of gases are represented by equations of state of which the simplest is that of ideal gases from this the density is given by ... 

The molar concentrations and densities of gases increase with decreasing volume. 

The Density of Gases activity (eCltapter 9.4) allows you to compare the densities of various gases at different temperatures and pressures. How does the density change when the pressure is increased Why does pressure affect density this way ... 

This requirement is fulfilled in gas chromatography (GC), where nitrogen or helium is used as the carrier gas. The low density of gases correlates with their high diffusion coefficients, and therefore in GC fast separations at high flow rates can be achieved when compared with LC. In Figure 7.2.1, the diffusion coefficient versus density diagram shows the areas occupied by the mobile phases in HPLC and GC. 

Understanding the densities of gases can be useful in the everyday world. For example, miners who drill deep into the ground must know which gases are present, and which have the highest densities. (See... 

Helium balloons and hot air balloons also depend on the density of gases. These objects are filled with gases that are less dense than air. Therefore, they are able to float. 

Density of Gases Dgas = molar mass/22.4 L c Specific Heat... 

AW propagation velocity is sensitive to changes in the density of any medium in contact vrith the substrate surface. Inspection of the mass-loading term for AW devices (Chapter 3 Equatirm 5.1) reveals an implicit dependence of wave velocity on the density of a coating layer. Note that a density change need not occur in a surface-immobilized film in order to be detected changes in the ambient medium produce an effect as well. TSM [61], SAW [11], and FPW devices have been utilized to monitor the pressure (via the density) of gases. 

The Density of a Perfect Gas. Since density is defined as the weiglit per unit volume, the general gas law can be used to calculate densities of gases at various temperatures and pressures. Solving the general gas law for Wt/Y... 

The density of a substance is the mass per unit volume of the substance (kg/m, g/cm Ibm/ft, etc.) The specific volume of a substance is the volume occupied by a unit mass of the substance it is the inverse of density. Densities of pure solids and liquids are essentially independent of pressure and vary relatively slightly with temperature. Hie temperature variation may be in either direction the density of liquid water, for example, increases from 0.999868 g/cm at 0°C to 1.00000 g/cm at 3.98°C, and then decreases to 0.95838 g/cm at 100°C. Densities of many pure compounds, solutions, and mixtures may be found in standard references (such as Perry s Chemical Engineers Handbook pp. 2-7 through 2-47 and 2-91 through 2-120). Methods of estimating densities of gases and mixtures of liquids are given in Chapter 5 of this book. 

Ki. K2 coefficients of uniformity of cellular saturation density of gase phase... 

The quantity of heat c which is necessary to raise the temperature of unit mass 1° C. at constant volume, is much more difficult to determine than the specific heat at constant pressure. Owing to the very low density of gases we should either have... 

The densities of gases are much lower than those of solids or liquids. 

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