Reactivity (chemistry)

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In chemistry, reactivity is the ability of a substance to enter into a chemical reaction . It is neither a thermodynamic nor a kinetic variable, but a qualitative term for the stability or reactivity of a substance. Stable substances are also classified as not very reactive.

Examples:

  1. If you put elemental potassium in normal air, it reacts e.g. T. with ignition with the humidity. Potassium has a high reactivity and is very reactive.
  2. If you put it under argon or petroleum ether , there is no noticeable reaction. Potassium has a low reactivity under argon and is therefore stable.
  3. The elements of the noble gases are particularly inert. Since they do not form any compounds, noble gases are always elementary.

If one wants to describe the reactivity in terms of physical quantities, it depends thermodynamically on the free enthalpy or Gibbs energy . In simple terms, this indicates how much energy is available for a substance to be released and is a substance property .

The kinetic variable corresponding to the reactivity in a reaction is called the activation energy . Roughly speaking, this is the energy that has to be applied to “get a reaction going” and thus determines the speed of the reaction . So it answers the question: "In what time is the energy released in this reaction?"

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