Ozone mole fraction

Latitude, degW Ozone Mole Fraction, ppm No. Cases at or above 0.080 ppm... 

Figure 3 shows the ratio of the values of Warnatz input coefficients to our corresponding values. This figure shows that at the higher temperatures (i.e., at the larger initial ozone mole fractions), the values for k and k2 differ markedly. The fact... 

Figure 1. Computed profiles for unity initial ozone mole fraction...

Figure 2. Comparison of experimental (Streng and Grosse) and computed burning velocities over a wide range of initial ozone mole fractions (O), this work (A), Warnatz (Hi), Streng and Grosse.

In comparing profiles there are sensible differences in some model results. For an initial ozone mole fraction of unity Figures 4 and 5 show a comparison of the atomic oxygen and temperature profile respectively. (For ease in viewing the curves have been arbitrarily displaced from each other along the distance axis.) Following the method of comparison discussed above we substitute Warnatz expressions for ki and k2 into our code and find the dashed-line profiles. Thus, we find that differences in the model profiles are due mainly to the different expressions for k and k2. 

In order to distinguish which expression for k2, if either, is correct, high temperature measurements and/or ab initio calculations of the rate coefficient for reaction (2) are required. Alternately, the computed differences in the values for atomic oxygen and for the temperature in the burned region at an initial ozone mole fraction of unity appear to be large enough that profile measurements above such a flame may be sufficient to distinguish between the two expressions. 

Figure 4. Calculated atomic oxygen profiles for unity initial ozone mole fraction (-----), the result of substituting Warnatz s expression for k, and k into our model.

Figure 5.12. Ozone mole fraction (ppmv) on the isobaric surface of 10 hPa measured by the LIMS instrument (Nimbus 7) on 24 January, 1979. Note the intrusion of subtropic ozone into the polar region during a planetary scale wave disturbance. Courtesy of L. Lyjak and J. Gille, NCAR.

Mole fractions, parts per million, and parts per billion all are ratios of moles of a particular substance to total moles of sample. Mole fraction is moles per mole, ppm is moles per million moles, and ppb Is moles per billion moles. These measures are related by scale factors ppm = 10 JT, and ppb = lO X - In other words, a concentration of 1 ppm is a mole fraction of 10 , and a concentration of 1 ppb is a mole fraction of 10. When the ozone concentration in the atmosphere reaches 0.5 ppm, the mole fraction of ozone is 0.5 X 10 , or 5 X 10. Example shows how to work with parts per million. 

The viscosity of the solution decreases rapidly as fluorine is added. A semilog plot of viscosity of the mole fraction gives a straight line at both temperatures which is typical of a nonassociated liquid. The surface tension of ozone is approximately three times that of oxygen. 

A small amount of starch solution is added as an indicator because it forms a deep-blue complex with the triiodide solution. Disappearance of the blue color thus signals the completion of the titration. Suppose 53.2 L of a gas mixture at a temperature of 18°C and a total pressure of 0.993 atm is passed through a solution of potassium iodide until the ozone in the mixture has reacted completely. The solution requires 26.2 mL of a 0.1359-M solution of thiosulfate ion to titrate to the endpoint. Calculate the mole fraction of ozone in the original gas sample. 

Thus, by choosing a set of wavelengths for which the cross section au is notably different, the mole fraction of the absorbant (proportional to c) can be retrieved at different altitudes. This method is commonly used to measure the vertical distribution of ozone in the stratosphere on the global scale. The vertical resolution, however, is not better than several kilometers. 

Figure 5.70. Upper panel Concentration (cm-3) of OH and HO2 as a function of the NOx (NO + NO2) mole fraction (pptv) for conditions representative of the upper troposphere (UT-solid line) and planetary boundary layer (PBL-dashed line). Lower panel Same, but for the net photochemical rate (ppb/hr) of ozone. The values corresponding to the upper troposphere are multiplied by 10. From Brune (2000).

Atmospheric chemistry is dominated by trace species, ranging in mixing ratios (mole fractions) from a few parts per million, for methane in the troposphere and ozone in the stratosphere, to hundredths of parts per trillion, or less, for highly reactive species such as the hydroxyl radical. It is also surprising that atmospheric condensed-phase material plays very important roles in atmospheric chemistry, since there is relatively so little of it. Atmospheric condensed-phase volume to gas-phase volume ratios range from about 3 x KT7 for tropospheric clouds to 3 x ICE14 for background stratospheric sulfate aerosol. 

The partial pressure of ozone can be calculated from the mole fraction and the total pressure. 

A mixture of gases occupies a volume of 53.2 L at 18 °C and 0.993 atm. The mixture is passed slowly through a solution containing an excess of KI to ensure that all the ozone reacts. The resulting solution requires 26.2 mL of 0.1359 M Na2S203 to titrate to the end point. Calculate the mole fraction of ozone in the original mixture. 

Let us use as an example one recent environmental case history relevant to petrochemicals production. Nitrous oxide (N2O) is implicated as a contributor to stratospheric ozone damage, and is also a potent greenhouse gas (Table 2.7). Recent work indicated that about 10% of the nitrous oxide contributions to the atmosphere was from the world s adipic acid plants, slightly more than the fraction contributed by biomass burning [31, 32]. It has been estimated that about 1 mol of N2O is produced per mole of adipic acid, or about 0.3 kg of N2O per kg of adipic acid. 

The fractions of the 1-ethoxyethoxy radicals undergoing reactions 1-4 are shown in Tables and compared with previous FllR studies and with theoretical estimates. Although diethyl ether is rapidly photo-oxidised, its contribution to tropospheric ozone formation is limited as one of the major products is ethyl formate which is relatively unreactive in the troposphere. This is also confirmed from the NO-NO2 oxidation stoichiometry, ca, 1 mole NO is oxidised per mole diethyl ether reacted. 

---