ALUMINIUM CHEMISTRY

Chemical reactions of aluminium

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Dive into the world of aluminium chemistry and its unique reactivity. Explore the fascinating reactions and non-reactivity of aluminium with various elements and compounds.

What does aluminum react with?

Simple substances:

  • halogens (fluorine, chlorine, bromine and iodine)
  • sulfur
  • phosphorus
  • nitrogen
  • carbon
  • oxygen (combustion)

Complex substances:

  • water
  • mineral acids (hydrochloric, phosphoric)
  • sulfuric acid
  • nitric acid
  • alkalis
  • oxidizers
  • oxides of less active metals (alumothermy)

What did not react aluminum with?

Aluminum does not react:

  • with hydrogen
  • under normal conditions, with concentrated sulfuric acid (due to passivation, the formation of a dense oxide film)
  • under normal conditions, with concentrated nitric acid (also due to passivation)

See also:. more on aluminium chemistry

Aluminium and air

Typically, the aluminium surface is always covered with a thin layer of aluminum oxide, which protects it from exposure to air, more precisely, oxygen. It is therefore considered, that aluminum does not react with air. If this oxide layer is damaged or removed, the fresh surface of aluminum reacts with oxygen in the air. Aluminum can burn in oxygen dazzling white flame to form aluminum oxide Al2O3.

Reaction of aluminum with oxygen:

  • 4Al + 3O2 —> 2Al2O3

Aluminum and water

Chemical reactions of aluminium with water according to the following reactions [2]:

  • 2Al + 6H2O = 2Al(OH)3 + 3H2 (1)
  • 2Al + 4H2O = 2AlO (OH) + 3H2 (2)
  • 2Al + 3H2O = Al2O3 + 3H2 (3)

As a result of these reactions are formed, respectively, following aluminium compounds:

  • modification of aluminum hydroxide bayerite and hydrogen (1)
  • modification of aluminum hydroxide bohemite and hydrogen (2)
  • aluminum oxide and hydrogen (3)

These reactions, by the way, are of great interest in the development of compact hydrogen generation systems for vehicles, which run on hydrogen [2].

All these reactions are thermodynamically possible at a temperature of from room temperature to the melting point of aluminum 660 oC. All of them are also exothermic, that is, they occur with the release of heat [2]:

  • At a temperature from room temperature to 280 ºС the most stable reaction product is Al (OH)3.
  • At a temperature of 280 to 480 ºС the most stable reaction product is AlO (OH).
  • At temperatures above 480 ºC most stable reaction product is Al2O3.

Thus, alumina Al2O3 It becomes thermodynamically more stable, than Al (OH)3 at an elevated temperature. The product of the reaction of aluminum with water at room temperature is aluminum hydroxide Al (OH)3.

Reaction (1) shows, that aluminum should spontaneously react with water at room temperature. However, in practice, a piece of aluminum, dropped into the water, It does not react with water at room temperature and even in boiling water. The thing is, that aluminum on the surface has a thin coherent layer of aluminum oxide Al2O3. This oxide film is held firmly on the aluminum surface and prevents its reaction with water. therefore, to start and maintain the reaction of aluminum with water at room temperature, it is necessary to constantly remove or destroy this oxide layer [2].

Aluminum and halogens

Aluminum reacts violently with all halogens:

  • fluorine F
  • chloro Cl
  • bromine Br
  • iodine I.

Reaction with hydrogen fluoride, chlorine, bromine and iodine:

  • 2Al + 3F2 → 2AlF3
  • 2Al + 3Cl2 → 2AlCl3
  • 2Al + 3Br2 → Al2Br6
  • 2Al + 3l2 → Al2I6

Aluminum and acid

Aluminum actively reacts with dilute acids: sulfuric, hydrochloric and nitric, with the formation of the corresponding salts: aluminium sulfate Al2SO4, aluminium chloride AlCl3 and aluminium nitrate Al (NO3)3.

Chemical reactions of aluminium with dilute acids:

  • 2Al + 3H2SO4 —> Al2(SO4)3 + 3H2
  • 2Al + 6HCl —> 2AlCl3 + 3H2
  • 2Al + 6HNO3 —> 2Al(NO3)3 + 3H2

Reactions of aluminium with concentrated sulfuric and hydrochloric acids:

  • does not interact at room temperature
  • reacts when heated to form a salt, oxides and water.

Aluminum and alkalis

Aluminum in an aqueous solution of alkali (sodium hydroxide) reacts to form sodium aluminate.

The reaction of aluminum with sodium hydroxide is:

  • 2Al + 2NaOH + 6H2O -> 2Na [Al (OH)4] + 3H2

All important reactions with aluminum

For completeness, we present a list of the main reactions involving aluminum from the fundamental book on aluminum [3]:

Sources:

1. Aluminium. Thirteenth Element. Encyclopedia – 2008

2. Reaction of Aluminum with Water to Produce Hydrogen /John Petrovic and George Thomas, U.S. Department of Energy, 2008

3. https://pilgaardelements.com/Aluminum/Reactions.htm