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Another type of binary phase diagram is a boiling-point diagram for a mixture of two components, i. e. chemical compounds. For two particular volatile components at a certain pressure such as atmospheric pressure , a boiling-point diagram shows what vapor (gas) compositions are in equilibrium with given liquid compositions depending on temperature.
A phase diagram showing the allotropes of iron, distinguishing between several different crystal structures including ferrite (α-iron) and austenite (γ-iron). Phase transitions can also occur when a solid changes to a different structure without changing its chemical makeup.
Wavy single bonds represent unknown or unspecified stereochemistry or a mixture of isomers. For example, the adjacent diagram shows the fructose molecule with a wavy bond to the HOCH 2 - group at the left. In this case the two possible ring structures are in chemical equilibrium with each other and also with the open-chain structure.
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 ...
The term sublimation refers specifically to a physical change of state and is not used to describe the transformation of a solid to a gas in a chemical reaction. For example, the dissociation on heating of solid ammonium chloride into hydrogen chloride and ammonia is not sublimation but a chemical reaction.
Transition state structures can be determined by searching for first-order saddle points on the potential energy surface (PES) of the chemical species of interest. [5] A first-order saddle point is a critical point of index one, that is, a position on the PES corresponding to a minimum in all directions except one.
Any chemical structure that lasts longer than the time for typical bond vibrations (10 −13 – 10 −14 s) can be considered as intermediate. [4] Figure 5:Potential Energy Surface and Corresponding 2-D Reaction Coordinate Diagram derived from the plane passing through the minimum energy pathway between A and C and passing through B
Theories of chemical structure were first developed by August Kekulé, Archibald Scott Couper, and Aleksandr Butlerov, among others, from about 1858. [4] These theories were first to state that chemical compounds are not a random cluster of atoms and functional groups, but rather had a definite order defined by the valency of the atoms composing the molecule, giving the molecules a three ...