Example Gases

A chemical reactivity hazard, as the term is used in this publication, is a situation with the potential for an uncontrolled chemical reaction that can result directly or indirectly in serious harm to people, property or the environment. The uncontrolled chemical reaction might be accompanied by a temperature increase, pressure increase, gas evolution or other form of energy release. It need not be explosive to result in serious harm. For example, gases evolved from a chemical reaction can be flammable, toxic, corrosive, hot, or can pressurize an enclosure to the point of rupture. 

For example, gases expand to fill the entire volume of any container in which you put them. Also, gases are easily compressed into smaller volumes. Even more so than liquids, gases easily form homogenous mixtures. Because so much open space occurs between individual gas particles, these particles cire pretty laid back about the idiosyncrasies of their neighbors. 

Primitive considerations convince us that such secondary forces exist. For example, gases consist of disordered molecules, whether they be polyatomic like chlorine or ether vapour, or single atoms like helium or mercury vapour. But all gases, even helium, ultimately condense to liquids — and then to solids — if they are cooled and/or compressed sufficiently. When the molecules are forced into close proximity and have their kinetic energies diminished, the weak intermolecular forces are able to take control. Liquefaction results. The strength of these forces can be measured by the latent heat necessary to evaporate the liquid, or to sublime the solid. The equation,... 

All other compounds (for example, gases, other covalent compounds, and all solids) either contain no ions or have ions that are affected by the presence of the other ions. These weak electrolytes, nonelectrolytes, or solids (ionic or not) are written using their regular formulas. 

With Emergence an similar phenomenon is discussed almost in all areas of science as an example, gases have characteristics like temperature or pressure, but the composing molecules do not have those characteristics. 

Table 4.2 shows the wide variation in values. For example, gases on the shell side (that is, on the outside of the tubes) have h values which are over an order of magnitude less than those for liquids flowing inside pipes. 

The Second Law of Thermodynamics is based on our experiences, as seen by the following examples. Gases mix spontaneously. When a drop of food coloring is added to a glass of water, it diffuses until a homogeneously colored solution results. When a truck is driven down the street, it consumes fuel and oxygen, producing carbon dioxide, water vapor, and other emitted substances. 

Another classification one could make is by looking at the medium the sensors are used for, for example gases, liquids, slurries, powders, etc. 

So far we have dealt with weU-defined, intuitively obvious phases gas, liquid solid. But chemical engineers deal with other, less intuitive phases of considerable technical interest and economic importance, for example gases and vapors adsorbed onto solids. Figure 11.21 shows, as an example the equilibrium curve (always called an adsorption isotherm or isotherm in the adsorption literature) for nitrogen adsorbed on zeolite at a temperature well below room temperature, but far above the critical temperature of nitrogen (126.2 K). 

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