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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.
In chemistry, metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts , such as metal nitrates , sulfates , and perchlorates .
Explosive reaction of sodium in water, shattering the glass vessel. The reaction can be extremely violent with alkali metals as the hydrogen gas catches fire. [2] Metals like gold and silver, which are below hydrogen in the reactivity series, do not react with water.
Likewise, the corrosion of most metals by oxygen is accelerated at low pH. Providing the electrons for the above reaction is the oxidation of iron that may be described as follows: Fe → Fe 2+ + 2 e −. The following redox reaction also occurs in the presence of water and is crucial to the formation of rust: 4 Fe 2+ + O 2 → 4 Fe 3+ + 2 O 2−
When finely powdered, magnesium reacts with water to produce hydrogen gas: Mg(s) + 2 H 2 O(g) → Mg(OH) 2 (aq) + H 2 (g) + 1203.6 kJ/mol. However, this reaction is much less dramatic than the reactions of the alkali metals with water, because the magnesium hydroxide builds up on the surface of the magnesium metal and inhibits further reaction ...
Paul Sabatier (1854-1941) winner of the Nobel Prize in Chemistry in 1912 and discoverer of the reaction in 1897. The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures (perhaps 3 MPa [1]) in the presence of a nickel catalyst.
Heterogeneous OER is sensitive to the surface which the reaction takes place and is also affected by the pH of the solution. The general mechanism for acidic and alkaline solutions is shown below. Under acidic conditions water binds to the surface with the irreversible removal of one electron and one proton to form a platinum hydroxide. [4]