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Elementary Reaction
An elementary reaction is a chemical reaction in which one or more chemical species react directly to form Product (chemistry), products in a single reaction step and with a single transition state. In practice, a reaction is assumed to be elementary if no reaction intermediates have been detected or need to be postulated to describe the reaction on a molecular scale. An apparently elementary reaction may be in fact a stepwise reaction, i.e. a complicated sequence of chemical reactions, with reaction intermediates of variable lifetimes. In a unimolecular elementary reaction, a molecule Dissociation (chemistry), dissociates or Isomerisation, isomerises to form the products(s) :\mbox \rightarrow \mbox At constant temperature, the reaction rate, rate of such a reaction is proportional to the concentration of the species :\frac=-k[\mbox]. In a bimolecular elementary reaction, two atoms, molecules, ions or Radical (chemistry), radicals, and , react together to form the product(s) :\ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reaction
A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, energy change as new products are generated. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the Atomic nucleus, nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive Chemical element, elements where both electronic and nuclear changes can occur. The substance (or substances) initially involved in a chemical reaction are called reagent, reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more Product (c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radical (chemistry)
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize. Most organic radicals have short lifetimes. A notable example of a radical is the hydroxyl radical (HO·), a molecule that has one unpaired electron on the oxygen atom. Two other examples are triplet oxygen and triplet carbene (꞉) which have two unpaired electrons. Radicals may be generated in a number of ways, but typical methods involve redox reactions. Ionizing radiation, heat, electrical discharges, and electrolysis are known to produce radicals. Radicals are intermediates in many chemical reactions, more so than is apparent from the balanced equations. Radicals are important in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes. A majority ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steady State (chemistry)
In chemistry, a steady state is a situation in which all state variables are constant in spite of ongoing processes that strive to change them. For an entire system to be at steady state, i.e. for all state variables of a system to be constant, there must be a flow through the system (compare mass balance). A simple example of such a system is the case of a bathtub with the tap running but with the drain unplugged: after a certain time, the water flows in and out at the same rate, so the water level (the state variable Volume) stabilizes and the system is in a steady state. The steady state concept is different from chemical equilibrium. Although both may create a situation where a concentration does not change, in a system at chemical equilibrium, the net reaction rate is zero ( products transform into reactants at the same rate as reactants transform into products), while no such limitation exists in the steady state concept. Indeed, there does not have to be a reaction a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rate Equation
In chemistry, the rate equation (also known as the rate law or empirical differential rate equation) is an Empirical relationship, empirical Differential equation, differential Expression (mathematics), mathematical expression for the reaction rate of a given reaction in terms of concentrations of chemical species and constant parameters (normally rate coefficients and partial orders of reaction) only. For many reactions, the initial rate is given by a power law such as :v_0\; =\; k[\mathrm]^x[\mathrm]^y where and are the molar concentrations of the species and usually in Mole (unit), moles per liter (molarity, ). The exponents and are the partial ''orders of reaction'' for and , respectively, and the ''overall'' reaction order is the sum of the exponents. These are often positive integers, but they may also be zero, fractional, or negative. The order of reaction is a number which quantifies the degree to which the rate of a chemical reaction depends on concentrations of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecularity
In chemistry, molecularity is the number of molecules that come together to react in an elementary (single-step) reactionAtkins, P.; de Paula, J. Physical Chemistry. Oxford University Press, 2014 and is equal to the sum of stoichiometric coefficients of reactants in the elementary reaction with effective collision ( sufficient energy) and correct orientation. Depending on how many molecules come together, a reaction can be unimolecular, bimolecular or even trimolecular. The kinetic order of any elementary reaction or reaction step is ''equal'' to its molecularity, and the rate equation of an elementary reaction can therefore be determined by inspection, from the molecularity. The kinetic order of a complex (multistep) reaction, however, is not necessarily equal to the number of molecules involved. The concept of molecularity is only useful to describe elementary reactions or steps. Unimolecular reactions In a unimolecular reaction, a single molecule rearranges atoms, forming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ideal Gases
An ideal gas is a theoretical gas composed of many randomly moving point particles that are not subject to interparticle interactions. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics. The requirement of zero interaction can often be relaxed if, for example, the interaction is perfectly elastic or regarded as point-like collisions. Under various conditions of temperature and pressure, many real gases behave qualitatively like an ideal gas where the gas molecules (or atoms for monatomic gas) play the role of the ideal particles. Many gases such as nitrogen, oxygen, hydrogen, noble gases, some heavier gases like carbon dioxide and mixtures such as air, can be treated as ideal gases within reasonable tolerances over a considerable parameter range around standard temperature and pressure. Generally, a gas behaves more like an ideal gas at higher temperature and lower pressure, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collision Theory
Collision theory is a principle of chemistry used to predict the rates of chemical reactions. It states that when suitable particles of the Reagent, reactant hit each other with the correct orientation, only a certain amount of collisions result in a perceptible or notable change; these successful changes are called successful collisions. The successful collisions must have enough energy, also known as activation energy, at the moment of impact to break the pre-existing bonds and form all new bonds. This results in the products of the reaction. The activation energy is often predicted using the transition state theory. Increasing the concentration of the reactant brings about more collisions and hence more successful collisions. Increasing the temperature increases the average kinetic energy of the molecules in a solution, increasing the number of collisions that have enough energy. Collision theory was proposed independently by Max Trautz in 1916 and William Lewis (physical chemis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cycloaddition
In organic chemistry, a cycloaddition is a chemical reaction in which "two or more Unsaturated hydrocarbon, unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of the Multiplicity (chemistry)#Molecules, bond multiplicity". The resulting reaction is a cyclization reaction. Many but not all cycloadditions are Concerted reaction, concerted and thus pericyclic. Nonconcerted cycloadditions are not pericyclic. As a class of addition reaction, cycloadditions permit carbon–carbon bond formation without the use of a nucleophile or electrophile. Cycloadditions can be described using two systems of notation. An older but still common notation is based on the size of linear arrangements of atoms in the reactants. It uses parentheses: where the variables are the numbers of linear atoms in each reactant. The product is a cycle of size . In this system, the standard Diels-Alder reaction is a (4 + 2)-cyc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peter Waage
Peter Waage (29 June 1833 – 13 January 1900) was a Norwegian chemist and professor of chemistry at the University of Kristiania. Along with his brother-in-law Cato Maximilian Guldberg, he co-discovered and developed the law of mass action between 1864 and 1879. Biography He grew up on the island of Hidra in Vest-Agder, Norway. He was the son of Peder Pedersen Waage (1796–1872) and Regine Lovise Wathne (1802–72). He attended the Bergen Cathedral School and studied chemistry and mineralogy at the University of Kristiania (now University of Oslo) under Adolph Strecker. In 1858, he received the Crown Prince's gold medal (''Kronprinsens gullmedalje'') for work on the development of a theory of oxygen-containing acid radicals. He became a cand.real. in 1859. He subsequently traveled to France and Germany, where he studied for two years including time spent with Robert Bunsen in Heidelberg. In 1861, Waage was made an associate professor and in 1866 he was app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cato Maximilian Guldberg
Cato Maximilian Guldberg (11 August 1836 – 14 January 1902) was a Norwegian mathematician and chemist. Guldberg is best known as a pioneer in physical chemistry. Background Guldberg was born on 11 August 1836, in Christiania. He was the eldest son of Carl August Guldberg (1812–92) and Hanna Sophie Theresia Bull (1810–54). He was the brother of nurse and educator Cathinka Guldberg as well as mathematician Axel Sophus Guldberg. He attended Aug. Holths private latinskole in Christiania. Guldberg studied mathematics and physics at the University of Christiania and took his diploma in 1859. That same year he received the Crown Prince's gold medal (''Kronprinsens gullmedalje'') for a dissertation in pure mathematics. He received a travel and education scholarship in 1861, studying applied mathematics and machine learning in what is now Germany, Switzerland and France. Career Guldberg first taught at Hartvig Nissens skole in Christiania. Gulberg worked at the Royal Frederic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Law Of Mass Action
In chemistry, the law of mass action is the proposition that the rate of a chemical reaction is directly proportional to the product of the activities or concentrations of the reactants. It explains and predicts behaviors of solutions in dynamic equilibrium. Specifically, it implies that for a chemical reaction mixture that is in equilibrium, the ratio between the concentration of reactants and products is constant. Two aspects are involved in the initial formulation of the law: 1) the equilibrium aspect, concerning the composition of a reaction mixture at equilibrium and 2) the kinetic aspect concerning the rate equations for elementary reactions. Both aspects stem from the research performed by Cato M. Guldberg and Peter Waage between 1864 and 1879 in which equilibrium constants were derived by using kinetic data and the rate equation which they had proposed. Guldberg and Waage also recognized that chemical equilibrium is a dynamic process in which rates of reaction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
