Gas Solution Research Articles

Assessing Secondary and College Students’ Implicit Assumptions about the Particulate Nature of Matter: Development and Validation of the Structure and Motion of Matter Survey

Development of learning progressions has been at the forefront of science education for several years. While understanding students' conceptual development toward big ideas in science is extremely valuable for researchers, science teachers can also benefit from assessment tools that diagnose their students' trajectories along the learning progressions. In this paper, we describe the develop- ment and validation of a teacher-friendly survey, the Structure and Motion of Matter (SAMM) survey, designed to measure students' trajectories along aspects of a research-based learning progression on the particulate nature of matter. Specifically, the survey assesses students' implicit assumptions about four concepts: the structure of solute and solvent substances in a gas solution, the origin of motion of gaseous solute particles, and their trajectories. The process to ensure the translation validity (face and content validity) of the survey is described. Criterion validity study results indicate that the SAMM survey is well grounded in theory, and the testretest study results indicate that the survey is also reliable. Finally, the development of an Excel-based scoring scheme associated with the SAMM survey is also described. Inter-rater reliability studies indicate that the scoring scheme can be used reliably.

Conformational Stability from Variable-Temperature Infrared Spectra of Xenon Solutions, r0 Structural Parameters, and Vibrational Assignment of Pyrrolidine

The infrared spectra of gaseous and variable-temperature liquid xenon solutions of pyrrolidine have been recorded. The enthalpy difference has been determined to be 109 ± 11 cm(-1) (1.30 ± 0.13 kJ mol(-1)) with the envelope-equatorial conformer more stable than the twist form with 37 ± 3% present at ambient temperature. Ab initio calculations utilizing various basis sets up to MP2(full)/aug-cc-pVTZ have been used to predict the conformational stabilities, energy at the equatorial-axial saddle point, and barriers to planarity. From previously reported microwave rotational constants along with MP2(full)/6-311+G(d,p) predicted structural values, adjusted r(0) parameters have been obtained for both conformers. Heavy atom distances (Å) of equatorial[twist] conformer are as follows: N(1)-C(2) = 1.469(3)[1.476(3)], N(1)-C(3) = 1.469(3)[1.479(3)], C(2)-C(4) = 1.541(3)[1.556(3)], C(3)-C(5) = 1.541(3)[1.544(3)], C(4)-C(5) = 1.556(3)[1.543(3)]; and angles (deg)∠N(1)C(2)C(4) = 102.5(5)[107.6(5)], ∠N(1)C(3)C(5) = 102.5(5)[105.4(5)], ∠C(2)C(4)C(5) = 104.3(5)[104.6(5)], ∠C(3)C(5)C(4) = 104.3(5)[103.7(5)], ∠C(2)N(1)C(3) = 104.1(5)[103.9(5)], τC(2)C(4)C(5)C(3) = 0.0(5)[13.5(5)]. A complete vibrational assignment is proposed for both conformers.

Enthalpy of solvation correlations for organic solutes and gases dissolved in 2-propanol, 2-butanol, 2-methyl-1-propanol and ethanol

Data have been assembled from the published literature on the enthalpies of solvation for 91 organic vapors and gaseous solutes in 2-propanol, for 73 gaseous compounds in 2-butanol, for 85 gaseous compounds in 2-methyl-1-propanol and for 128 gaseous compounds in ethanol. It is shown that an Abraham solvation equation with five descriptors can be used to correlate the experimental solvation enthalpies to within standard deviations of 2.25 kJ/mole, 1.99 kJ/mole, 1.73 kJ/mole and 2.54 kJ/mole for 2-propanol, 2-butanol, 2-methyl-1-propanol and ethanol, respectively. The derived correlations provide very accurate mathematical descriptions of the measured enthalpy of solvation data at 298 K, which in the case of ethanol span a range of 136 kJ/mole. Division of the experimental values into a training set and a test set shows that there is no bias in predictions, and that the predictive capability of the correlations is better than 3.5 kJ/mole.

Experimental Investigation of Reactive Absorption of Ammonia and Carbon Dioxide by Carbonated Ammonia Solution

In this work, reactive absorption of gases in aqueous electrolyte solutions has been investigated resulting in the development of a procedure in order to calculate the concentrations of ionic and molecular species in the liquid phase. Two duplicate experiments were conducted to investigate simultaneous reactive absorption of ammonia and carbon dioxide in partially carbonated ammonia solutions. The experiments were carried out employing an absorption pilot plant. The compositions of the electrolytes (ammonia and carbon dioxide groups) have been determined using principle knowledge of electrolyte solutions. The results revealed that the concentrations of ionic and molecular species in the liquid phase drastically influence the absorption rates of ammonia and carbon dioxide.

Simultaneous absorption of carbon dioxide, sulfur dioxide and nitrogen dioxide into aqueous 2-amino-2-methy-1-propanol

The absorption mechanism of three acidic gases in alkali solution, such as the system of carbon dioxide, sulfur dioxide, and nitrogen dioxide in 2-amino-2-methyl-1-propanol (AMP), was used to predict the simultaneous absorption rates using the film theory. Diffusivity, Henry constant and mass transfer coefficient of each gas were used to obtain the theoretical enhancement factor of each component. The theoretical molar fluxe of each gas was obtained by an approximate solution of mass balances with reaction regions of the first order reaction of CO2 and instantaneous reactions of SO2 and NO2 in CO2-SO2-NO2-AMP system. From the comparison between the theoretical total fluxes of these gases and the measured ones, the solubility and the reaction rate between each gas and AMP influenced its molar flux.

Enthalpy of solvation correlations for organic solutes and gases dissolved in 1-propanol and tetrahydrofuran

Data have been assembled from the published literature on the enthalpies of solvation for 103 organic vapors and gaseous solutes in 1-propanol and for 86 gaseous compounds in tetrahydrofuran. It is shown that an Abraham solvation equation with five descriptors can be used to correlate the experimental solvation enthalpies to within standard deviations of 2.35 kJ/mole and 2.10 kJ/mole for 1-propanol and tetrahydrofuran, respectively. The derived correlations provide very accurate mathematical descriptions of the measured enthalpy of solvation data at 298 K, which in the case of 1-propanol span a range of 119 kJ/mole. Division of the experimental values into a training set and a test set shows that there is no bias in predictions, and that the predictive capability of the correlations is better than 3.5 kJ/mole.

Influence of groundwater flowpaths, residence times and nutrients on the extent of microbial methanogenesis in coal beds: Powder River Basin, USA

Water and natural gas samples were collected from coalbed methane wells and a surface coal mine in the Powder River Basin (PRB) and analyzed for solute chemistry, isotopes, and gas composition to test hypotheses about the timing and source of recharge, importance of nutrient influx, and extent of microbial methanogenesis in coalbeds. Recharge to the Wyodak–Anderson coal zone in the central portions of the PRB appears to be from the southern basin margin based on δ 18O–H 2O values and hydraulic gradients. Coal zones along the eastern margin, near the coal outcrop, represent mixing between surface water and deeper circulating groundwater. Coalbeds along the northwestern basin margin may contain high elevation recharge from the Bighorn Mountains, with flow patterns likely affected by local faults. Detectable 14C (0.39 to 4.13 pmC) in coal waters throughout the PRB indicates they were recharged < 50,000 BP. Correlation of δD–CH 4 and δD–H 2O values suggests that methane has accumulated since the Late Pleistocene. Nutrient concentrations (C, N and P species) are low throughout the PRB and do not correlate to groundwater flowpaths or methanogenic pathways; nutrients may be sourced from in-situ leaching of coals. Carbon isotope values of CH 4 and CO 2 likely indicate the extent of methanogenesis (i.e. early versus late stage), rather than the dominant metabolic pathway (i.e. acetate fermentation versus CO 2 reduction). Coal gasses from the northwestern margin of the basin are isotopically depleted and suggest “early stage” methanogenesis, where the reactant carbon reservoir has not been significantly fractionated due to relatively rapid groundwater flow. Coal gasses from the central basin and southeastern margin are isotopically enriched and suggest “late stage” methanogenesis where the reactant carbon reservoir has been significantly depleted likely due to longer groundwater residence times.

Analysis and Improvement of an Experiment on Diffusion Rate of Gases Introduced in High School Chemistry Textbooks

This study is to analyze the problems observed in the experiment on ‘diffusion rate of gases’ in high school Chemistry II text books and investigate the reason followed by suggestion of an improved experimental method. As typically introduced in textbooks, a few drops of HCl(aq) and NH3(aq) were dropped at both ends of a glass tube, and then the position of ammonium chloride white ring created by the reaction with HCl(g) and NH3(g) was measured. The position of the white ring changed with time. In order to investigate the reason of such change, the experiment was repeated using HCl and NH3 gases, and the position of white ring did not changed with time. Meanwhile, the relative diffusion distance did not match with the theoretical expectation of the Graham's diffusion experiment but did with that of the Loschmidt's diffusion experiment. Based on this result experimental condition allowing equal partial pressure of HCl and NH3 gases in hydrochloric acid and aqueous ammonia solution, respectively was found, and under the obtained condition the position of white ring did not change and was consistent with the theoretical expectation. This study is anticipated to help learners to understand the scientific concept of diffusion through the improved experiment.

10.2478/s11814-009-0185-8

Modeling of solubility of acid gases in aqueous alkanolamine solutions is essential for design of an absorber for natural gas sweetening. In this work an apparatus similar to the device of Hayduk and Chen (1970), which was improved by Pahlavanzadeh and Motahhari (1997), for the measurement of gas solubility data by the synthetic method was used. The solubility of hydrogen sulfide in aqueous diisopropanolamine (DIPA) solution in mass concentration range of 30–40% for 101,325 Pa pressure and for temperature ranging from 313–343 K was reported. The obtained experimental solubility data of H2S in aqueous solutions of DIPA was used to predict the different interaction parameters of modified UNIQUAC-NRF model for calculating the activity coefficients. For nonideality of species in liquid phase, the UNIQUAC-NRF equation with ion-pair approach was applied. For long range interaction, the Pitzer-Debye-Huckel term was used.

The excited state dipole moments of betaine pyridinium investigated by an innovative solvatochromic analysis and TDDFT calculations

This work reports on the solvatochromic properties of a simple heterocyclic betaine pyridinium, 2-(1-pyridinio)benzimidazolate (SBPa), having promising potentialities in non-linear optics. From advanced PCM-TDDFT calculations, the solvatochromism of SBPa was found to be unusual, involving two different electronic states for absorption (S(0)→ S(2)) and emission (S(1)→S'(0)). To account for this behavior, we developed an innovative physical treatment which consists in a non-linear fit of the solvatochromic data using the Bilot-Kawski theoretical model and visualizing the least-square coefficient χ(2) on a 2D map as a function of the solute polarizability and gas phase absorption energy. In parallel, Kamlet-Taft correlations were undertaken to select a propitious set of electrostatic solvents usable in this treatment. Protic solvents that lead to specific interactions and nonpolar solvents that favor dimerization processes were excluded. From a choice of aprotic solvents with sufficiently high polarity, 4 dipole moments μ(g)(S(0)) = +9.1 D, μ(e)(S(2)) = -1.5 D, μ(e)(S(1)) = 0 D and μ(g)(S'(0)) = +3.31 D were determined, the 3 former values being in close agreement with TDDFT values, although the solute polarizability values seem underestimated. Anyhow, disregarding this discrepancy, we evaluated the static hyperpolarizability to β(0) = -64 × 10(-30) esu from the solvatochromic data in close agreement with DFT calculations.

Prediction of gas solubilities in ionic liquids

Ionic liquids (of which it is estimated that there are at least one million simple fluids) generate a rich chemical space, which is now just at the beginning of its systematic exploration. Many properties of ionic liquids are truly unique and, which is more important, can be finely tuned. Differential solubility of industrial chemicals in ionic liquids is particularly interesting, because it can be a basis for novel, efficient, environmentally friendly technologies. Given the vast number of potential ionic liquids, and the impossibility of a comprehensive empirical exploration, it is essential to extract the maximum information from extant data. We report here some computational models of gas solubility. These multiple regression- and neural network-based models cover a chemical space spanned by 48 ionic liquids and 23 industrially important gases. Molecular polarisabilities and special Lewis acidity and basicity descriptors calculated for the ionic liquid cations and anions, as well as for the gaseous solutes, are used as input parameters. The quality of fit "observed versus predicted Henry's law constants" is particularly good for the neural network model. Validation was established with an external dataset, again with a high quality fit. In contrast to many other neural network models published, our model is no "black box", since contributions of the parameters and their nonlinearity characteristics are calculated and analysed.

Prediction of hydrogen solubility in heavy hydrocarbons over a range of temperatures and pressures using molecular dynamics simulations

Using the method of molecular dynamics (MD), we have estimated the solubility of hydrogen in heavy hydrocarbons for a range of temperatures and pressures. Heavy hydrocarbon systems are known to be challenging not only for experimental measurements but also for reliable estimations using traditional equations of state (EOS). The simulation system used was designed with semi-permeable membranes to mimic actual experimental studies of gas solubility. Binary interaction parameters between the solute gas and the solvent (heavy hydrocarbons) components were adjusted when necessary to improve agreement with experimental results and then used in subsequent multi-component studies. Temperature and pressure ranges studied included higher temperatures and pressures which are especially difficult to investigate experimentally. Simulation results were finally used to adjust the binary interaction parameters (BIP) in simulation packages (e.g. Aspen) to enable quick and reliable predictions.

Phase equilibria in chemical reactive fluid mixtures

Downstream processing is a major part of nearly all processes in the chemical industries. Most separation processes in the chemical (and related) industries for fluid mixtures are based on phase equilibrium phenomena. The majority of separation processes can be modelled assuming that chemical reactions are of no (or very minor) importance, i.e., assuming that the overall speciation remains unchanged during a separation process. However, there are also a large number of industrially important processes where the thermodynamic properties are influenced by chemical reactions. The phase equilibrium of chemical reactive mixtures has been a major research area of the author’s group over nearly 40 years. In this contribution, three examples from that research are discussed. The first example deals with the vapour phase dimerisation of carboxylic acids and its consequences on phase equilibrium phenomena and phase equilibrium predictions. The second example deals with the solubility of sour gases ( e.g., carbon dioxide and sulfur dioxide) in aqueous solutions of ammonia. That topic has been of interest for many years, e.g., in relation with the gasification and liquefaction of coal and, more recently, with the removal of carbon dioxide from flue gas in the “chilled ammonia process”. The third example deals with phase equilibrium phenomena in aqueous solutions of polyelectrolytes. It deals with the phenomenon of “counter ion condensation” and methods to model the Gibbs free energy of such solutions.

The role of non-CO2 greenhouse gases in cost-effective strategies to reduce pollution by dairy cattle in the Czech Republic

Agriculture is an important source of greenhouse gases, including methane (CH4) and nitrous oxide (N2O). In addition, it is a source of compounds contributing to other environmental problems such as acidification, terrestrial and aquatic eutrophication, tropospheric ozone formation, and human health problems. These compounds include, for instance, ammonia (NH3), nitrogen oxides (NOx), and particulate matter (PM) volatile organic compounds or nitrate (). In this article, we address the question how we can reduce the overall environmental impact (OEI) of agriculture at least costs, and what the role of non-CO2 greenhouse gases in these optimal solutions is. We present results of the DAIRY model, an optimization model for the Czech dairy production sector. The model distinguishes between nine study regions defined according environmental and agriculture characteristics and calculates emissions, their potential impact and OEI at regional and national level. We show that in cost-effective scenarios the model tends to select measures to reduce emissions contributing to climate change and aquatic eutrophication first. This is in contrast with current policies in the Czech Republic, which is aiming at reduction of emissions causing acidification and eutrophication. We also show that reducing greenhouse gas emissions plays a modest role in optimal strategies to reduce the OEI of dairy production.

Kinetics of Methane Desorption from Coal Nano- and Mesostructures

Kinetics of gas desorption from a material with a developed nano- and mesostructure is studied by the example of methane in coal. It is supposed that the solute gas passes from coal fragments to capillaries by solid-state diffusion and then proceeds to the outer volume by filtration. Desorption is found to occur in three stages. Estimations of the duration of these stages are given. Comparing the sorption experiments with the theory developed here is the suggested way to evaluate the size of the fragments comprising the system, as well as the closed porosity and gas solubility in the studied porous material.

Mathematical correlations for describing enthalpies of solvation of organic vapors and gaseous solutes into ionic liquid solvents

Previously reported ion-specific equation coefficients for the Abraham general solvation model are updated using recently published enthalpy of solution data for organic solutes dissolved in room temperature ionic liquids (RTILs). Reported for the first time are equation coefficients for 1-hexyloxymethyl-3-methylimidazolium, 1,3-dihexyloxymethylimidazolium, 3-methyl-N-butylpyridinium, tris(pentafluoroethyl)trifluoro phosphate, and tetracyanoborate ions. In total 12 sets of cation-specific and 10 sets of anion-specific equation coefficients have been determined for each model. The derived correlations describe the 942 experimental enthalpies of solvation to within a standard deviation of about 1.65 kJ/mol.

A Theoretical Analysis of Dissolved-Gas Transfer to the Bulk Liquid in Gas Absorption with a First-Order Reaction

A theoretical analysis using the surface-renewal and film-penetration models, which includes gas-phase resistance to mass transfer, is presented for the rate of absorption of a gas and its transfer to the bulk liquid in the case where the solute gas undergoes a first-order chemical reaction in the liquid phase. It reveals that: a. The fraction of absorbed gas transported to the bulk liquid depends upon the Hatta number Ha in case of the surface-renewal model and on Ha as well as a dimensionless hydrodynamic parameter in case of the film-penetration model. b. The widely assumed law of addition of resistances is valid for the surface-renewal and film-penetration models. c. The reaction influences both the overall mass-transfer coefficient and the nature of the driving force, i.e. the increased rate of absorption due to the reaction is not solely due to the enhancement factor multiplying the liquid-phase mass-transfer coefficient for physical absorption as has been conventionally assumed in the literature. It is also shown that in a gas-liquid reactor the film and surface-renewal models give close predictions for both the rate of absorption and concentration of dissolved gas in the liquid leaving the reactor. For values of Ha ⩾ 0.5, the bulk-liquid concentration of dissolved gas predicted by both models is negligible compared to its interfacial concentration.

Physicochemical approach to nanobubble solutions

Abstract Small bubbles of nitrogen, methane, or argon with an average radius of 50 nm, as measured by scanning electron microscopy, were prepared under atmospheric conditions. The lifetime of the nanobubbles extended to more than two weeks. The total amount of gases in the nanobubble solutions reached 600 cm 3 per 1 dm 3 of water, and the liquid density was about 0.988 g/cm 3 . The internal pressure of the nanobubbles was estimated to be 6 MPa. The number of nanobubbles was 1.9×10 16 bubbles per 1 dm 3 of water. These findings show that almost no gas samples are dissolved homogeneously in the aqueous solution and that the vast majority is present in the form of nanobubbles, that is, nanobubbles should be thermodynamically unstable. Attenuated total reflectance infrared spectroscopy showed that the surfaces of the nanobubbles contain hard hydrogen bonds that may reduce the diffusivity of gases through the interfacial film.

Absorption kinetics of NO from simulated flue gas using Fe(II)EDTA solutions

The absorption of NO encountering flue gases in aqueous solutions of Fe(II)EDTA was determined using a semi-batch stirred tank with a plane gas–liquid interface at 50 °C. The concentrations of NO, SO 2 and O 2 in the feeding stream were 300–800 ppm, 500–2200 ppm and 0–20%, respectively. The pH value of the Fe(II)EDTA solutions varied from 3 to 11. The concentrations of Fe(II)EDTA were maintained between 0.01 and 0.05 M. Experiments were performed to evaluate the effect of operating parameters on the NO absorption rate, the reaction kinetics of the reactants in gas and liquid phases, and the effect of competition between various reactants on the mass transfer rate in the NO removal system. Results indicate that the average reaction rate constant is 3.70 × 10 7 M −1 s −1. Adding NaOH does not increase the absorption capability of Fe(II)EDTA. The presence of O 2 decreases the NO absorption rate with Fe(II)EDTA. The absorption rate of NO with Fe(II)EDTA decreases at low concentrations of SO 2, but increases at high concentrations.

Measurement and modeling of solubility of H2S in aqueous diisopropanolamine solution

Modeling of solubility of acid gases in aqueous alkanolamine solutions is essential for design of an ab- sorber for natural gas sweetening. In this work an apparatus similar to the device of Hayduk and Chen (1970), which was improved by Pahlavanzadeh and Motahhari (1997), for the measurement of gas solubility data by the synthetic method was used. The solubility of hydrogen sulfide in aqueous diisopropanolamine (DIPA) solution in mass con- centration range of 30-40% for 101,325 Pa pressure and for temperature ranging from 313-343 K was reported. The obtained experimental solubility data of H2S in aqueous solutions of DIPA was used to predict the different interaction parameters of modified UNIQUAC-NRF model for calculating the activity coefficients. For nonideality of species in liquid phase, the UNIQUAC-NRF equation with ion-pair approach was applied. For long range interaction, the Pitzer- Debye-Huckel term was used.