Mass standard conditions

For calculation of the volumetric flow rate only the cross section area of the pipe is to be known. In order to give flow under standard conditions the temperature and pressure must be measured, and for conversion to mass flow the composition or density of the gas must be determined. These process parameters are often monitored by calibrated instrumentation. 

Density and Relative Density. Density is mass per unit volume and in SI is normally expressed as kilograms per cubic meter (density of water = 1000 kg/m or 1 g/cm ). The term specific gravity was formerly the accepted dimensionless value describing the ratio of the density of sohds and Hquids to the density of water at 4°C or for gases to the density of ak at standard conditions. The term specific gravity is being replaced by relative mass density, a more descriptive term. 

Mass concentration units for ambient measurements are mass (/xg) per unit volume (m ). Size classification involves the use of specially designed inlet configurations, e.g., PMjq sampling. To determine mass concentration, all the particles are removed from a known volume of air and their total mass is measured. This removal is accomplished by two techniques, filtration and impaction, described in Chapter 13. Mass measurements are made by pre-and postweighing of filters or impaction surfaces. To account for the absorption of water vapor, the filters are generally equilibrated at standard conditions T = 20°C and 50% relative humidity). 

Meters are accurate within close limits as legislation demands. However, gas is metered on a volume basis rather than a mass basis and is thus subject to variation with temperature and pressure. The Imperial Standard Conditions are 60°F, 30inHg, saturated (15.56°C, 1913.7405 mbar, saturated). Gas Tariff sales are not normally corrected, but sales on a contract basis are. Correction may be for pressure only on a fixed factor basis based on Boyle s Law or, for larger loads, over 190,000 therms per annum for both temperature and pressure using electronic (formerly mechanical) correctors. For high pressures, the compressibility factor Z may also be relevant. The current generation of correctors corrects for pressure on an absolute basis taking into account barometric pressure. 

Radium-226 decays by alpha emission to radon-222. Suppose that 25.0% of the energy given offby one gram of radium is converted to electrical energy. What is the minimum mass of lithium that would be needed for the voltaic cell Li Li+1 Cu2+ Cu, at standard conditions, to produce the same amount of electrical work (AG°) ... 

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. 

It can be assumed that the gas mixture follows ideal gas behavior and that the kilogram molar mass of a gas occupies 22.4 m3 at standard conditions of 0°C and 1 atm (1.013 bar)... 

Assume that the mixture of benzene and toluene obeys Raoult s Law and the molar mass in kilograms occupies 22.4 m3 in the vapor phase at standard conditions. The molar masses of benzene and toluene are 78 and 92 respectively. The vapor pressures of benzene and toluene at 25°C are 0.126 bar and 0.0376 bar respectively. 

Assume the molar mass in kilograms occupies 22.4 m3 at standard conditions and the plant operates for 8600 h y... 

It can be assumed that the molar mass in kilograms at standard conditions occupies 22.4 m3. The vapor pressures of toluene can be represented by ... 

A gas turbine with power output of 10.7 MW and an efficiency of 32.5% burns natural gas. In order to reduce the NOx emissions to the environmental limits, 0.6 kg steam is injected into the combustion per kg of fuel. The airflow through the gas turbine is 41.6 kg-s 1. The composition of the natural gas can be assumed to be effectively 100% methane with a molar mass of 16 kg-kmoU1. The kilogram molecular volume can be assumed to occupy 22.4 m3 at standard conditions. 

According to the combined gas law, the volume of a given mass of gas can have any value, depending on its temperature and pressure. To compare the quantities of gas present in two different samples, it is useful to adopt a set of standard conditions of temperature and pressure. By universal agreement, the standard temperature is chosen as 273 K (0°C) and the standard pressure is chosen as exactly 1 atm (760torr). Together, these conditions are referred to as standard conditions or as standard temperature and pressure (STP). While there is nothing special about STP, some authors and some instructors find it convenient to use this short notation for this particular temperature and pressure. 

The mass spectrometer is a very sensitive and selective instrument. However, the introduction of the eluent into the vacuum chamber and the resulting significant pressure drop reduces the sensitivity. The gas exhaust power of a normal vacuum pump is some 10 ml min-1 so high capacity or turbo vacuum pumps are usually needed. The gas-phase volume corresponding to 1 ml of liquid is 176 ml for -hexane, 384 ml for ethanol, 429 ml for acetonitrile, 554 ml for methanol, and 1245 ml for water under standard conditions (0°C, 1 atmosphere). The elimination of the mobile phase solvent is therefore important, otherwise the expanding eluent will destroy the vacuum in the detector. Several methods to accomplish this have been developed. The commercialized interfaces are thermo-spray, moving-belt, electrospray ionization, ion-spray, and atmospheric pressure ionization. The influence of the eluent is very complex, and the modification of eluent components and the selection of an interface are therefore important. Micro-liquid chromatography is suitable for this detector, due to its very small flow rate (usually only 10 p min - ). 

Provided El spectra have been measured under some sort of standard conditions (70 eV, ion source at 150-250 °C, pressure in the order of 10 " Pa), they exhibit very good reproducibility. This is not only the case for repeated measurements on the same instrument, but also between mass spectrometers having different types of mass analyzers, and/or coming from different manufacturers. This property soon led to the collection of large El mass spectral libraries, either printed [76-78] or computerized. [79] The best established El mass spectral databases are the NIST/EPA/NIH Mass Spectral Database and the Wiley/NBS Mass Spectral Database, each of them giving access to about 120,000 evaluated spectra. [80-83]... 

Figure 2-1 shows that the reversible cell potential for a fuel cell consuming H2 and O2 decreases by 0.27 mV/°C under standard conditions where the reaction product is water vapor. However, as is the case in PAFC s, an increase in temperature improves cell performance because activation polarization, mass transfer polarization, and ohmic losses are reduced. 

Every chemical reaction reaches after a time a state of equilibrium in which the forward and back reactions proceed at the same speed. The law of mass action describes the concentrations of the educts (A, B) and products (C, D) in equilibrium. The equilibrium constant K is directly related to the change in free enthalpy G involved in the reaction (see p.l6) under standard conditions (AG° = - R T In K). For any given concentrations, the lower equation applies. At AG < 0, the reaction proceeds spontaneously for as long as it takes for equilibrium to be reached (i.e., until AG = 0). At AG > 0, a spontaneous reaction is no longer possible (endergonic case see p.l6). In biochemistry, AG is usually related to pH 7, and this is indicated by the prime symbol (AG° or AG ). 

The course of electron transfer reactions (redox reactions, see p. 14) also follows the law of mass action. For a single redox system (see p.32), the Nernst equation applies (top). The electron transfer potential of a redox system (i. e., its tendency to give off or take up electrons) is given by its redox potential E (in standard conditions, E° or E° ). The lower the... 

Other complications are that the reactor feed may be preheated and the feed pressure may vary, and thus the volumetric flow rate of gases will be functions of the reactor temperature and pressure at fixed mass flow rate. Therefore, the space velocity of gases is frequently defined at standard conditions T = 25°C and P = 1 atm. 

Ca is a comparatively difficult element for the body to absorb and digest. It is essentially only available for consumption associated with various other moieties (e.g., citrate, phosphate, and other anions). Each Ca source has unique physical, structural, and chemical properties such as mass, density, coordination chemistry, and solubility that are largely determined by the anions associated with the Ca +. Aqueous solubility of various Ca salts can vary markedly and comparisons are frequently made under standardized conditions. The water solubility of CCM is moderate when ranked versus other Ca sources frequently used as dietary supplements and food/beverage fortificants. The solubility of CCM (6 2 3 molar ratio) is 1.10-g salt in 100 ml of H2O at 25 °C (Fox et ah, 1993a). Table 6.4 lists the solubility of various Ca sources in water at specific temperatures, and also includes some information on potential sensory characteristics. 

In our development studies, Endeavor (5 mL) and Buchi (IL) reactor systems were used to screen catalysts and to evaluate the impurity profile under various process conditions. Elydrogenation kinetic studies were carried out using a 100 mL EZ-seal autoclave with an automatic data acquisition system to monitor the hydrogen uptake and to collect samples for HPLC analysis. Standard conditions of 5 g of aldehyde in 25 mL ethyl acetate and 25 mL methanol with 0.5 g of 5%Pd/C Engelhard Escat 142 were used in this investigation. For the Schiff s base formation and subsequent hydrogenation, inline FTTR was used to follow the kinetics of the Schiff s base formation under different conditions. Tables 1 and 2 show the changes in the substrate concentration under different conditions. Both experiments were carried without any limitations of gas-liquid mass transfer. 

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