Concentration of a gas

Increasing or decreasing the partial pressure of a gas is the same as increasing or decreasing its concentration. The effect on a reaction s equilibrium position can be analyzed as described in the preceding example for aqueous solutes. Since the concentration of a gas depends on its partial pressure, and not on the total pressure of the system, adding or removing an inert gas has no effect on the equilibrium position of a gas-phase reaction. 

Electrochemistry plays an important role in the large domain of. sensors, especially for gas analysis, that turn the chemical concentration of a gas component into an electrical signal. The longest-established sensors of this kind depend on superionic conductors, notably stabilised zirconia. The most important is probably the oxygen sensor used for analysing automobile exhaust gases (Figure 11.10). The space on one side of a solid-oxide electrolyte is filled with the gas to be analysed, the other side... 

Flammable limits The minimum and maximum concentrations of a gas or vapor in air which can be ignited and sustain a self-propagating flame. 

The ideal gas equation (Equation ) can be rearranged to show that the concentration of a gas, which is moles of gas... 

LEL (lower explosive, OR FLAMMABLE, LIMIT) The minimum concentration of a gas, vapour, mist or dust in air at a given pressure and temperature that will propagate a flame when exposed to an efficient ignition source. Generally expressed as % by volume for gases and vapours, and as mg/m for mists or dusts. 

Langmuir s research on how oxygen gas deteriorated the tungsten filaments of light bulbs led to a theory of adsorption that relates the surface concentration of a gas to its pressure above the surface (1915). This, together with Taylor s concept of active sites on the surface of a catalyst, enabled Hinshelwood in around 1927 to formulate the Langmuir-Hinshelwood kinetics that we still use today to describe catalytic reactions. Indeed, research in catalysis was synonymous with kinetic analysis... 

The maximum and minimum concentrations of a gas, vapor, mist, spray, or dust in the air or other gaseous oxidant for a stable detonation to occur are the so-called upper and lower detonation limits. These limits depend on the size and geometry of the surroundings as well as other factors. Therefore, detonation limits found in the literature should be used with caution. Detonation limits are sometimes confused with deflagration limits and the term explosive limits is then used inconsiderately [40]. 

The New Jersey Department of Environmental Protection uses the TXDS method of consequence analysis to estimate potentially catastrophic quantities of toxic substances, as required by the New Jersey Toxic Catastrophe Prevention Act (TCPA). An acute toxic concentration (ATC) is defined as the concentration of a gas or vapor of a toxic substance that will result in acute health effects in the affected population and 1 fatality out of 20 or less (5% or more) during a 1-hr exposure. ATC values, as proposed by the New Jersey Department of Environmental Protection, are estimated for 103 extraordinarily hazardous substances and are based on the lowest value of one of the following (1) the lowest reported lethal concentration (LCLO) value for animal test data, (2) the median lethal concentration (LC50) value from animal test data multiplied by 0.1, or (3) the IDLH value. 

Since the concentration of a gas is proportional to its partial pressure (Dalton s law) Fa and Fe can be substituted for some more familiar units... 

Bunsen solubility coefficient (a ) The term that relates the concentration of a gas in seawater to its partial pressure in the atmosphere. It is dependent on temperature and salinity. 

Saturated (1) Of a solution containing the equilibrium concentrations of solutes dictated by the solubility of a particular solid. As a result, the mass of the solid in solution will remain constant over time. (2) Of a solution that contains the equilibrium concentration of a gas. This concentration is determined by the temperature and ionic strength (salinity) of the solution and the partial pressure of the gas in the atmosphere. 

Variation of Surface Tension of an Adsorbent Related to the surface excess concentration of a gas by the relation. 

Henry s law states that the concentration of a gas dissolved in a liquid is proportional to the pressure of the gas. This law is a consequence of the equilibrium... 

Solution We omit solids from the reaction quotient, and the concentration of a gas is expressed as the pressure of the gas. Therefore, the Nemst equation is... 

The molar concentration of a gas and a related quantity, the density of a gas, are both of great interest to meteorologists as well as to engineers. As we saw in Section G, the molar concentration is the number of moles of molecules divided by the volume of the sample (n/V). It follows from the ideal gas law that, for a gas behaving ideally,... 

The equilibrium concentration of a gas in the aqueous phase is directly proportional to the pressure of that gas—this is referred to as Henry s law of equilibrium distribution, defined as Pi = Kq P/. ... 

Some of these criteria help to explain the greater success of chromatographic reactors over adsorptive reactors for the gas phase reactions described here. They also point to a niche (if somewhat trivial) application of adsorptive reactors in end-of-pipe environmental processes, in which low concentrations of a gas-borne pollutant are adsorbed from waste gas over a long period before being destroyed by catalytic oxidation in a high-temperature regeneration step utilizing the heat liberated by combustion by means of a gas recycle. 

Here x is a parameter that characterizes the state of the system (for example, the concentration of a gas). Stability in equilibrium plane requires that the second derivative of the entropy be negative... 

So far we have been describing equilibria involving gases in terms of concentrations. Equilibria involving gases can also be described in terms of pressures. The relationship between the pressure and the concentration of a gas can be seen from the ideal gas equation ... 

The concentration of a gas dissolved in a liquid is inversely proportional to Henry s constant. Therefore, the larger the Henry s constant, the smaller the concentration of dissolved gases in the liquid. 

A second application to organometallic chemistry is related to NMR observation under high gas pressure. It makes it possible to strongly increase the concentration of a gas in a solution, to shift chemical equilibria and to detect intermediates under conditions similar to those used in homogenous catalysis. 

The fugacity of a gas in water is usually calculated from measurements of the gas concentration by using the above relation. The concentration of a gas in surface waters is at solubility equilibrium with the atmosphere (saturation) when the fugacities of the atmosphere and water are equal... 

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