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Water-reactive substances [1] are those that spontaneously undergo a chemical reaction with water, often noted as generating flammable gas. [2] Some are highly reducing in nature. [ 3 ] Notable examples include alkali metals , lithium through caesium , and alkaline earth metals , magnesium through barium .
Metal aqua ions are often involved in the formation of complexes. The reaction may be written as pM x+ (aq) + qL y− → [M p L q] (px-qy)+ In reality this is a substitution reaction in which one or more water molecules from the first hydration shell of the metal ion are replaced by ligands, L. The complex is described as an inner-sphere complex.
The alkali metals also react with water to form strongly alkaline hydroxides and thus should be handled with great care. The heavier alkali metals react more vigorously than the lighter ones; for example, when dropped into water, caesium produces a larger explosion than potassium if the same number of moles of each metal is used.
In fact, the rate of reaction of alkali metals (as evidenced by their reaction with water for example) is a function not only of position within the group but also of particle size. Hydrogen does not react with oxygen—even though the equilibrium constant is very large—unless a flame initiates the radical reaction, which leads to an explosion.
Solvated electrons are involved in the reaction of alkali metals with water, even though the solvated electron has only a fleeting existence. [10] Below pH = 9.6 the hydrated electron reacts with the hydronium ion giving atomic hydrogen, which in turn can react with the hydrated electron giving hydroxide ion and usual molecular hydrogen H 2. [11]
A Coulomb explosion is a "cold" alternative to the dominant laser etching technique of thermal ablation, which depends on local heating, melting, and vaporization of molecules and atoms using less-intense beams.
Batteries damaged by fire or salt water can explode and can take a long time to put out because of the lingering chain reaction inside the battery - something that also causes them to occasionally ...
If alkali builds up due to ion exchange, and remains on the surface of the glass, the decay process will accelerate. The presence of sodium or potassium ions in the alkali build up will increase the pH on the surface of the glass, causing it to become basic. This will dissolve silica from the glass as well as releasing more alkali ions. [10] [7]