|
Oscillating Reaction
In chemistry, a chemical oscillator is a complex mixture of reacting chemical compounds in which the concentration of one or more components exhibits periodic changes. They are a class of reactions that serve as an example of non-equilibrium thermodynamics with far-from-equilibrium behavior. The reactions are theoretically important in that they show that chemical reactions do not have to be dominated by equilibrium thermodynamic behavior. In cases where one of the reagents has a visible color, periodic color changes can be observed. Examples of oscillating reactions are the Belousov–Zhabotinsky reaction (BZ reaction), the Briggs–Rauscher reaction, and the Bray–Liebhafsky reaction. History The earliest scientific evidence that such reactions can oscillate was met with extreme scepticism. In 1828, G.T. Fechner published a report of oscillations in a chemical system. He described an electrochemical cell that produced an oscillating current. In 1899, W. Ostwald observed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bzr Fotos
Bzr may refer to: * GNU Bazaar * Benzodiazepine receptor The GABAA receptor (GABAAR) is an ionotropic receptor and ligand-gated ion channel. Its endogenous Ligand (biochemistry), ligand is γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system. Accurate regul ... (also known as the GABAA receptor) * Béziers Cap d'Agde Airport * Toyota Levin/Trueno BZ-R {{Disambig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gibbs Free Energy
In thermodynamics, the Gibbs free energy (or Gibbs energy as the recommended name; symbol is a thermodynamic potential that can be used to calculate the maximum amount of Work (thermodynamics), work, other than Work (thermodynamics)#Pressure–volume work, pressure–volume work, that may be performed by a closed system, thermodynamically closed system at constant temperature and pressure. It also provides a necessary condition for processes such as chemical reactions that may occur under these conditions. The Gibbs free energy is expressed as G(p,T) = U + pV - TS = H - TS where: * U is the internal energy of the system * H is the enthalpy of the system * S is the entropy of the system * T is the temperature of the system * V is the volume of the system * p is the pressure of the system (which must be equal to that of the surroundings for mechanical equilibrium). The Gibbs free energy change (, measured in joules in International System of Units, SI) is the ''maximum'' amount of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Propanedioic Acid
Malonic acid is a dicarboxylic acid with structure CH2(COOH)2. The ionized form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid's diethyl ester. The name originates from the Greek word μᾶλον (''malon'') meaning 'apple'. History Malonic acid is a naturally occurring substance found in many fruits and vegetables. There is a suggestion that citrus fruits produced in organic farming contain higher levels of malonic acid than fruits produced in conventional agriculture. Malonic acid was first prepared in 1858 by the French chemist Victor Dessaignes via the oxidation of malic acid. Hermann Kolbe and Hugo Müller independently discovered how to synthesize malonic acid from propionic acid, and decided to publish their results back-to-back in the Chemical Society journal in 1864. This led to priority dispute with Hans Hübner and Maxwell Simpson who had independently published preliminary results on related ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cerium(IV) Sulfate
Cerium(IV) sulfate, also called ceric sulfate, is an inorganic compound. It exists as the anhydrous salt Ce( SO4)2 as well as a few hydrated forms: Ce(SO4)2(H2O)x, with x equal to 4, 8, or 12. These salts are yellow to yellow/orange solids that are moderately soluble in water and dilute acids. Its neutral solutions slowly decompose, depositing the light yellow oxide CeO2. Solutions of ceric sulfate have a strong yellow color. The tetrahydrate loses water when heated to 180-200 °C. It is insoluble in glacial acetic acid and pure (96%) ethanol. It was historically produced by direct reaction of fine, calcined cerium (IV) oxide and concentrated sulfuric acid, yielding the tetrahydrate. Uses The ceric ion is a strong oxidizer, especially under acidic conditions. If ceric sulfate is added to dilute hydrochloric acid, then elemental chlorine is formed, albeit slowly. With stronger reducing agents it reacts much faster. For example, with sulfite in acidic environments it reacts ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potassium Bromate
Potassium bromate () is a bromate of potassium and takes the form of white crystals or powder. It is a strong oxidizing agent. Preparation and structure Potassium bromate is produced when bromine is passed through a hot solution of potassium hydroxide. This first forms unstable potassium hypobromite, which quickly disproportionates into bromide and bromate: : 3 \ \xrightarrow\ 2 + Electrolysis of potassium bromide solutions will also give bromate. Both processes are analogous to those used in the production of chlorates. Potassium bromate is readily separated from the potassium bromide present in both methods owing to its much lower solubility; when a solution containing potassium bromate and bromide is cooled to 0°C, nearly all bromate will precipitate, while nearly all of the bromide will stay in solution. As established by X-ray crystallography, the O-Br-O angles are 104.5°, consistent with its pyramidal shape of the anion. The Br-O distances are 1.66 Å. Uses in b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boris Pavlovich Belousov
Boris Pavlovich Belousov (; 19 February 1893 – 12 June 1970) was a Soviet chemist and biophysicist who discovered the Belousov–Zhabotinsky reaction (BZ reaction) in the early 1950s. His work initiated the field of modern nonlinear chemical dynamics. The Belousov family had strong anti-Tsarist sympathies and, after the Russian Revolution of 1905, they were arrested and later forced to leave the country. They settled in Switzerland, where Boris studied chemistry in Zürich. Returning to Russia at the beginning of World War I,Ник. ГорькавыйСказка о химике Белоусове, который изготовил жидкие часы Ж. НиЖ №2, 2011 г. Belousov tried to join the army, but was denied for health reasons. He took up a job in a military lab under the direction of the chemist Vladimir Ipatiev. His value to the institute is indicated by the high military rank, Brigade Commander, roughly corresponding to General, that he attained. After ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self Organization
Self-organization, also called spontaneous order in the social sciences, is a process where some form of overall order arises from local interactions between parts of an initially disordered system. The process can be spontaneous when sufficient energy is available, not needing control by any external agent. It is often triggered by seemingly random fluctuations, amplified by positive feedback. The resulting organization is wholly decentralized, distributed over all the components of the system. As such, the organization is typically robust and able to survive or self-repair substantial perturbation. Chaos theory discusses self-organization in terms of islands of predictability in a sea of chaotic unpredictability. Self-organization occurs in many physical, chemical, biological, robotic, and cognitive systems. Examples of self-organization include crystallization, thermal convection of fluids, chemical oscillator, chemical oscillation, animal swarming, neural circuits, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Clock
A chemical clock (or clock reaction) is a complex mixture of reacting chemical compounds in which the onset of an observable property (discoloration or coloration) occurs after a predictable induction time due to the presence of clock species at a detectable amount. In cases where one of the reagents has a visible color, crossing a concentration threshold can lead to an abrupt color change after a reproducible time lapse. Types Clock reactions may be classified into three or four types: Substrate-depletive clock reaction The simplest clock reaction featuring two reactions: :A → C (rate k1) :B + C → products (rate k2, fast) When substrate (B) is present, the clock species (C) is quickly consumed in the second reaction. Only when substrate B is all used up or depleted, species C can build up in amount causing the color to change. An example for this clock reaction is the sulfite/iodate reaction or iodine clock reaction, also known as Landolt's reaction. Sometimes, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bromine
Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between those of chlorine and iodine. Isolated independently by two chemists, Carl Jacob Löwig (in 1825) and Antoine Jérôme Balard (in 1826), its name was derived , referring to its sharp and pungent smell. Elemental bromine is very reactive and thus does not occur as a free element in nature. Instead, it can be isolated from colourless soluble crystalline mineral halide Ionic salt, salts analogous to table salt, a property it shares with the other halogens. While it is rather rare in the Earth's crust, the high solubility of the bromide ion (Br) has caused its Bromine cycle, accumulation in the oceans. Commercially the element is easily extracted from brine evaporation ponds, mostly in the United States and Israel. The mass of bromine in the oce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Washington State University
Washington State University (WSU, or colloquially Wazzu) is a Public university, public Land-grant university, land-grant research university in Pullman, Washington, United States. Founded in 1890, WSU is also one of the oldest Land-grant university, land-grant universities in the Western United States, American West. With an undergraduate enrollment of 24,278 and a total enrollment of 28,581, it is the second largest institution of higher education in Washington state behind the University of Washington. It is Carnegie Classification of Institutions of Higher Education, classified among "R1: Doctoral Universities – Very high research activity". The WSU Pullman campus stands on a hill and is characterized by open spaces and a red brick and basalt material palette—materials originally found on site. The university sits within the rolling topography of the Palouse in rural eastern Washington and remains closely connected to the town and the region. The university also operat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oregonator
The Oregonator is a theoretical model for a type of autocatalytic reaction. The Oregonator is the simplest realistic model of the chemical dynamics of the oscillatory Belousov–Zhabotinsky reaction. It was created by Richard Field and Richard M. Noyes at the University of Oregon. It is a portmanteau of Oregon and oscillator. Earlier, the Brusselator model was proposed by Ilya Prigogine and his collaborators at the Free University of Brussels as a portmanteau of Brussels and oscillator. The Oregonator is a reduced model of the FKN mechanism (developed by Richard Field, Endre Kőrös Endre Kőrös (September 18, 1927 – February 18, 2002) was a Hungarian chemist mostly known in the field of nonlinear chemical dynamics for developing the FKN mechanism, a description of the Belousov–Zhabotinsky reaction involving 11 react ..., and Richard M. Noyes) which still involved 11 reactions and 12 species (21 intermediate species and 18 elementary steps). The Oregonator is chara ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brusselator
The Brusselator is a theoretical model for a type of autocatalytic reaction. The Brusselator model was proposed by Ilya Prigogine and his collaborators at the Université Libre de Bruxelles. It is a portmanteau of Brussels and oscillator. It is characterized by the reactions : A \rightarrow X : 2X + Y \rightarrow 3X : B + X \rightarrow Y + D : X \rightarrow E Under conditions where A and B are in vast excess and can thus be modeled at constant concentration, the rate equations become :\left\ = \left\ + \left\^2 \left\ - \left\ \left\ - \left\ \, :\left\ = \left\ \left\ - \left\^2 \left\ \, where, for convenience, the rate constants have been set to 1. The Brusselator has a fixed point at :\left\ = A \, :\left\ = \,. The fixed point becomes unstable when : B>1+A^2 \, leading to an oscillation of the system. Unlike the Lotka–Volterra equation, the oscillations of the Brusselator do not depend on the amount of reactant present initially ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
