Pure materials, calculating densities/concentrations

Another frequent mistake among students is to try to apply the ideal gas law to calculate the concentrations of species in condensed-matter phases (e.g., liquid or solid phases). Do not make this mistake] The ideal gas law only applies to gases. To calculate concentrations for liquid or solid species, information about the density (pj) of the liquid or solid phase is required. Both mass densities and molar densities (concentrations) as well as molar and atomic volumes may be of interest. The complexity of calculating these quantities tends to increase with the complexity of the material under consideration. In this section, we will consider three levels of increasing complexity pure materials, simple compounds or dilute solutions, and more complex materials involving mixtures of multiple phases/compounds. 

Mass densities (g/cm ) are readily available for most pure materials. For example, the density of Si is psi = 2.33 g/cm while the density of Si02 is Psi02 2.65 g/cm. Calculating the molar densities (molar concentrations) and molar volumes of pure Si and pure Si02 (or any other pure material) from their mass densities and their molecular weights is quite straightforward ... 

Then with the help of the precision micrometer, we determined the thicknesses of the obtained samples and their volumes were calculated using the known values of the thickness and diameter. The sample mass was measured by the precision analytical balance. The known sample volume and mass allowed us to find the density of the nanocomposite material. By this way it was possible to determine the dependencies of the material density on the molding temperature. These dependencies are presented in Figure 7.3 for the following samples pure modified low-density polyethylene (1), and nanocomposite materials based on low-density polyethylene matrix with 10% concentration of nanoparticles CdS (2) and MnO (3). 

Reactor physic studies for the transmutation of Am in separate subassemblies of a LMFR were made using a rather high Am-concentration (to restrict the number of the special assemblies), a typical fast reactor flux (3.61589 x 10 K/cm s) and depleted UOj as a. .matrix material. The calculations were done as fundamental mode bumup calculations with the KAPROS code system. The results show that for an irradiation cycle of 6 years the total amount of Am is halved, % of the original mass was fissioned and the remaining Vi transmuted mainly to Pu 238, Pu 242 and to Cm (242 and 244) and only a small percentage of the depleted UOj was fissioned. The power densities for varying Am and U contents could be adjusted between 500 W/cm (pure UOj) and about 1200 W/cm (pure Am... 

To verify that the quantity of leached salt was dependent on the area exposed to the pure water, a test was conducted in which only half the surface area was exposed. The results presented in Fig. 10.11 show that the amount of cerium is limited by the sample area exposed to the solution. With an assumed density of the coating material of 1.5 g/cm, the amount of cerium provided by the coating material could be calculated. The results of this calculation have been related to the maximum concentration of cerium detected by ICP in Table 10.3. The fraction of detected material was in the vicinity of about 50% in all cases. No dominant influence of agitation could be concluded from these data. 

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