).
Amedeo Avogadro also added to the understanding of chemical reactions. He said that all gasses at the same pressure, volume and temperature contain the same number of particles. This idea took a long time to be accepted. His ideas lead to the subscripts used in the formulas for gasses.
From the work of these and many other chemists, we now have a mostly complete knowledge of chemical reactions. There are now many classification systems to classify the different types of reactions. These include decomposition, polymerization, chain reactions, substitute reactions, elimination reactions, addition reactions, ionic reactions, and oxidation-reduction reactions.
Decomposition reactions are reactions in which a substance breaks into smaller parts. As an example, ammonium carbonate will decompose into ammonia, carbon dioxide, and water. Polymerization reactions are reactions in which simpler substances combine to form a complex substance. The thing that makes this reaction unusual is that the final product is composed of hundreds of the simpler reagent (a substance that contributes to a chemical reaction) species. One example is the polymerization of terephthalic acid with ethylene glycol to form the polymer called Dacron, a fibre, or Mylar, in sheet form:.
nH2OC(C6H4)CO2H + nHOCH2CH2OH -> [.OC(C6H4)CO2CH2CH2O.]n 2nH2O.
in which n is a large number of moles. A chain reaction is a series of smaller reactions in which the previous reaction forms a reagent for the next reaction. The synthesis of hydrogen bromide is a good example: .
H2 + Br2 -> 2HBr.
This is a simple equation that doesn't properly prove the reaction. It is very complex and starts with this: .
Br2 -> 2Br .
The next three reactions are related and should be grouped together. A substation reaction is a reaction in which a substance loses one or more atoms and replaces them with the same number of atoms of another element from another substance. Here is the example of chloroform that reacts with antimony triflouride:.