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Fundamental concepts
Published in W. John Rankin, Chemical Thermodynamics, 2019
When more than one component is present in a system the state of the system is not completely specified unless the relative amounts of the components are known. Of the various methods possible – mass percent, volume percent, kilograms per cubic metre, etc. – in most cases mole fraction is the most useful for expressing composition for thermodynamic purposes. Consider a system consisting of components A, B, … . The mole fraction of component B is defined as:
Overview
Published in James F. Pankow, Aquatic Chemistry Concepts, 2019
The mole fraction concentration scale can be used for gas mixtures, liquid solutions, and solid solutions. In most aqueous solutions of interest in this text, the mole fraction of liquid water xw is sufficiently close to 1.0 to assume that xw = 1. For gases, the reader has surely already made calculations based on the principle that in an ideal gas system, for each of the different gaseous constituents, the partial pressure of each constituent equals the mole fraction multiplied by the total pressure. In the case of N2(g) in the atmosphere, we have pN2=xN2Ptot
Basic Chemical Thermodynamics and Kinetics
Published in Kalliat T. Valsaraj, Elizabeth M. Melvin, Principles of Environmental Thermodynamics and Kinetics, 2018
Kalliat T. Valsaraj, Elizabeth M. Melvin
Environmental concentrations (air, soil, water) are expressed in a variety of units (Appendix D). Traditional units such as parts per million (ppm), parts per billion (ppb), and parts per trillion (ppt) are still in use, although these units are inexact and of dubious applicability. Chemical thermodynamicists prefer to work in mole fraction, molality, and molarity units.“Mole fraction” is defined as the ratio of the number of moles of a solute to the total number of moles of all species in the mixture, that is, xi=ni∑ini“Molarity” is the moles of solute per liter (dm3) of the mixture.“Molality” is the moles of solute per kilogram of the pure phase.The different concentration units are shown in Table 2.4. Other applicable and relevant units are derived from these basic units for all natural phases.
Experimental investigation on the degradation of polymer-containing oily sludge in sub-/supercritical water
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Pai Peng, Gaoyun Wang, Linhu Li, Hui Ge, Hui Jin, Liejin Guo
In this paper, the conversion rate (CR) represents the proportion of PCOS feedstock convert to aqueous and gas products. The yield of mixture of solid and oil (YS+O), gaseous products (YG), and liquid products (YL) is defined as follows. Mole fraction is used to express the composition of gaseous products. WF is the weight of PCOS feedstock, WG is the weight of gaseous products and WS+O represents the dry weight of the mixture of solid and oil. For describing the distribution of carbon and nitrogen in each phase, the distribution ratio is defined as follows. X represents C or N, and the subscript (i) is G, L, S, and O represents the phase of gas, liquid, solid residue, and oil, respectively.
True Gaussian mixture regression and genetic algorithm-based optimization with constraints for direct inverse analysis
Published in Science and Technology of Advanced Materials: Methods, 2022
In (1), mole fractions possess values between 0 and 1, where upper and lower limits are necessary for synthesis conditions, such as temperature and pressure, depending upon the constraints of an equipment. Examples of variables that have only 0 or 1 in (2) are dummy variables, such as presence or absence of an additive, washing, and pretreatment of raw materials. All categorical variables can be represented using dummy variables. Variables with values other than 1 can be converted to 0 or 1 by scaling. In (3), when considering mole fractions of raw materials while mixing several raw materials, it is necessary to total them up to 1. Some sets of variables can have different total values. As given in (4), the total value of several variables are required to be in a certain range.