A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds between atoms, and can often be described by a chemical equation.
The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of action is part of the reaction mechanism. Chemical reactions are described with chemical equations, which graphically present the starting materials, end products, and sometimes intermediate products and reaction conditions.
Chemical reactions happen at a characteristic reaction rate at a given temperature and chemical concentration, and rapid reactions are often described as spontaneous, requiring no input of extra energy other than thermal energy. Non-spontaneous reactions run so slowly that they are considered to require the input of some type of additional energy (such as extra heat, light or electricity) in order to proceed to completion (chemical equilibrium) at human time scales.
Different chemical reactions are used in combinations during in chemical synthesis in order to obtain a desired product. In biochemistry, a similar series of chemical reactions form metabolic pathways. These reactions are often catalyzed by protein enzymes. These enzymes increase the rates of biochemical reactions, so that metabolic syntheses and decompositions impossible under ordinary conditions may be performed at the temperatures and concentrations present within a cell.
The general concept of a chemical reaction has been extended to non-chemical reactions between entities smaller than atoms, including nuclear reactions, radioactive decays, and reactions between elementary particles as described by quantum field theory.
Read more about Chemical Reaction: History, Equations, Elementary Reactions, Chemical Equilibrium, Thermodynamics, Kinetics, Catalysis, Reactions in Organic Chemistry, Biochemical Reactions, Applications, Monitoring
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... Mechanisms of monitoring chemical reactions depend strongly on the reaction rate ... is introduction of a radioactive isotope into the reaction and monitoring how it changes over time and where it moves to this method is often used to ... Faster reactions are usually studied with ultrafast laser spectroscopy where utilization of femtosecond lasers allows short-lived transition states to be monitored at time scaled down to a few femtoseconds ...
... A sensitizer in chemoluminescence is a chemical compound, capable of light emission after it has received energy from a molecule, which became excited previously in the chemical reaction ... and a concentrated solution of hydrogen peroxide are mixed, a reaction occurs ClO-(aq) + H2O2(aq) → O2*(g) + H+(aq) + Cl-(aq) + OH-(aq) O2*is excited oxygen ... Hence, oxygen produced by this chemical reaction somehow 'absorbed' the energy released by the reaction and became excited ...
... Chemical reaction-based garments have cloth pouches or pockets where single-use packages of chemical hand warmers can be inserted ... The hand warmers are about the size of a package of cards, and they contain chemicals which produce heat ... these packs are exposed to air, an exothermic chemical reaction occurs, which provides several hours of heat ...
... In its simplest form, this chemical reaction is as follows 2 FeS2 + 9 O2 + 4 H2O → 8 H+ + 4 SO42− + 2 Fe(OH)3 (solid) The product Fe(OH)3, iron(III) hydroxide (orange), precipitates as a solid ... Other products of the chemical reaction are Hydrogen sulfide (H2S), a smelly gas Sulfur (S), a yellow solid Iron(II) sulfide (FeS), a black/gray/blue solid Hematite (Fe2O3), a red solid Goethite (FeO.OH), a ...
... The overall reaction is The reaction can be considered as a strong base catalysed, water facilitated reaction ...
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