Theory of van der Waals-Platteeuw model
Modifications to the well-known van der Waals-Platteeuw (VDW-P) model (van der Waals and Platteeuw, 1959) led to several thermodynamic models for predicting hydrate formation and/or dissociation conditions. The VDW-P model was derived which was based on the similarity between the hydrate formation and Langmuir adsorption. However, both the mechanisms are different, even if the adsorption mechanism is able to explain the nonstoichiometric feature of hydrates.
A brief discussion on the VDW-P hydrate model
Following were the assumptions based on which VDW-P model was developed. A cavity can have at most one guest gas molecule. Applicability of the ideal gas partition function is for the guest molecules. A pair of potential function is used to describe the interaction between guest and water molecules and cavity is considered as
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The first step is a quasi-chemical reaction for the formation of a stoichiometric basic hydrate and the second step is the physical adsorption for filling the empty linked cavities by gas molecules by applying Langmuir adsorption theory, resulting into the non-stoichiometric property of hydrate.
In the first step, following Sloan (1990), we assume that clusters formed when the gas molecules are dissolved in water and each guest molecule is surrounded by several water molecules. These clusters come together resulting into a basic hydrate, which is a combination of a basic cavities and linked cavities. Here, the basic cavities are fully occupied by the gas molecules, leaving linked cavities unfilled (empty cavity) and hydrate becomes stoichiometric. Following complex reaction descries the above process H2O + λ2G → Gλ2 .H2O
Where G stands for the gas species and λ2 is the number of basic cavities (large cavities) per water molecules. During this step basic hydrate encases the linked cavities in
The first step in the mechanism is preparing the positively charged NO2 from the HNO3 and H2SO4. This process occurs “in situ” meaning in the reaction mixture.
In our experiment we utilized the hydrate cobaltous chloride. Hydrates are crystalline compounds in which one or more molecules of water are combined with each unit of a salt. Cobalt (II) chloride hexahydrate is an inorganic compound which is a deep rose color in its hydrated form. As an inducer of
We thank the University of Oklahoma and the chemistry faculty for providing the space, instructions, and equipment for the development of this report and experiment.
When in solution, the hydronium and chloride ions formed will be partially surrounded by water molecules via ion-dipole bonds, an electrostatic force of attraction that exists between charges in the ions and the partial charges in the water molecules. Water molecules surrounding ions is called hydration.
The explicit presentation of the mathematics involved in the Arrhenius equation (Michels, Tsong, and Smith 1983) rendered the parameters involved in glass hydration understandable. However, the actual implementation of the physical processes described in the mathematical equations into a model replicating the natural environment is a complicated problem hard to solve (Stevenson 1998).
Quasar, Gian J. "Methane Hydrates." Methane Hydrates. Bermuda Triangle Org., n.d. Web. 28 Apr. 2014. .
enclosure is driven by the strength of the hydrogen bonds between the water molecules, leading
1. If gas bubbles form then fermentation occurred. Glucose. Carbon dioxide. The enzyme didn’t recognize the structure of glactose, because of the orientation of the H and OH on the carbon 4 is different than glucose. The enzyme only identifies very specific substances.
Niels Bohr's model of the hydrogen atom, was the primary reason for the understanding of energy levels.Bohr was able to explain the bright line spectrum of hydrogen. Sparked by the recent discovery of the diffraction patterns, scientists believed electrons could be described as waves. Bohr hypothesized that energy is being added to the hydrogen gas in the electricity form, and then leaving the gas in the form of light. He figured the light rays to be quantized, meaning only certain frequencies of the light rays can be seen. In turn, he reasoned that the hydrogen atoms themselves were quantized and, that they only can exist in certain energy levels. When the atoms absorb specific amounts of energy, they exist for a small period of time in higher energy levels. But as soon as these atoms lose their energy, they move back down to the lower levels of energy. His theory went on to state how the hydrogen atom can move up and down the energy levels, one level at a time, and can never stop in between. Every hydrogen atom is made up of a single electron - proton system. Because the negative electron is attracted to the positive proton, potential energy is created inside the atom.He figured that the farther away the electron is from the proton, the greater the potential energy is inside. In conclusion, since hydrogen atoms emit light energy in specific frequencies, the hydrogen atom must be within a specific energy level and nothing else. The different wavelengths help to determine the different colors emitted from the atom. The greater the wavelength, the faster the atom can be filled and jump to a higher level.Bohr developed his theory after studying the work of Einstein's ideas on the photons of energy.
When the hydrochloric acid was poured into marble chips, gas bubbles were seen – signifying the carbon dioxide (gas) that was being produced due to the chemical reaction.
The bonding nature of both ionic and molecular compounds will show that the materials produced tend to have many different properti...
It mainly exists as H2C2O4.2H2O, which is known as oxalic acid dihydrate. The 2H2O attached to the oxalic acid means that for every one molecule of Oxalic acid there is, there will be 2 molecules of water. This makes it predictable and allows for the standardization of NaOH. The reaction between NaOH and Oxalic acid dihydrate is as follows:
π is equal to the osmotic pressure, V is equal to the cell volume and B is the intracellular solids (Hall). Ponder’s R value is the ratio of intracellular solvent volume to the water in its environment; R=(Vi -b)/W. These two equations are related because Ponder’s R value is a measure of how much of an osmometer a cell is while the van’t Hoff relation shows what the osmotic pressure is, both inside and outside the cell. Overall cell membrane permeability can be measured by Ponder’s R value while the osmotic pressure differentials between the external environment and the internal environment are seen with the van’t Hoff relation (Hall). Cells evolved to become great osmometers, but not perfect osmometers, in order to provide a way for solutes to move along permeable membranes. The van’t Hoff relation permits organisms to live in environments of varying osmolarity because regulating solute concentration within a cell can increase or decrease the cell’s affinity for osmosis (Darnell et al). Ponder’s R value, on the other hand, shows how a cell can never become a perfect osmometer. If a cell could become a perfect osmometer, it could cause cell lysis or shrinkage of the cell (Hall). The avoidance of perfect osmometry can be seen within the human erythrocyte as a small portion of cell water will not take part in an osmotic exchange due to tonicity within its
The reaction which occurs is a neutralization reaction because the H+ and OH- ions react to form water.
Physical properties of compounds remain an interesting and important area of research since last century. Various physical properties of a compound are depending on vibrations of atoms present in it. Lattice dynamics is considered to be an important tool in studying these atomic vibrations. Lattice dynamical study of a compound gives information about the nature of inter-atomic forces present and helps to understand its bonding and structural properties.