Chemical Reactions Essay

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Title: Chemical Reactions Chemical Reactions A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, heat, light or electricity. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions. Equations Chemical equations are used to graphically illustrate chemical reactions. They consist of chemical or structural formulas of the reactants. They are separated by an arrow which indicates the direction and type of the reaction. The tip of the arrow points in the direction in which the reaction proceeds. A double arrow pointing in opposite directions is used for equilibrium reactions. Equations should be balanced according to the number of atoms of each species should be the same on both sides of the equation. This is achieved by scaling the number of involved molecules by the appropriate integers a, b, c and d. Elementary reactions The elementary reaction is the smallest division into which a chemical reaction can be decomposed to, it has no intermediate products. Most experimentally observed reactions are built up from many elementary reactions that occur in parallel or sequentially. The actual sequence of the individual elementary reactions is known as reaction mechanism. An elementary reaction involves a few molecules, usually one or two, because of the low probability for several molecules to meet at a certain time. Kinetics The speed at which a reaction takes place is studied by reaction

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