Reactivity of Aluminium


Aluminium is very light (nearly three times less dense than iron) yet possesses high tensile strength. These properties make up its substantial usage in the transportation industries, in the construction of aircraft, ships as well as cars.


It is extremely reactive, though the metal is secured by a surface layer of inert transparent oxide (Al2O3) that creates quickly in the air, providing excellent rust resistance. A few of its important reactions are discussed in this article.

Reaction with Air

When a piece of aluminium sheet is exposed to moist air it obtains a thin, continual layer of aluminium oxide, which prevents more attacks on the metal by atmospheric oxygen and water under normal conditions.

Because of this aluminium sheets are stated to be corrosion-free. However, if the aluminium powder is heated to 800 ° C or above, the metal will react with air to form aluminium oxide, Al2O3, and aluminium nitride, AIN.

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The reaction is accompanied by the development of heat and intense white light. This characteristic of aluminium is utilized in flashlight photography.

4 Al (s) + 3 O2 (g) à 2 Al2O3 (s)

2 Al (s) + N2 (g) à 2Al N (s)

As a result of its capability to incorporate both oxygen and also nitrogen, the metal is often used to remove air bubbles from liquified or molten metals. Salt solutions corrode aluminium severely so aluminium and aluminium alloys are not suitable for marine usage.

Reaction with Non-Metals

Heated aluminium integrates with the halogens, sulphur, nitrogen, phosphorus and carbon, accompanied by the formation of heat.

2 Al (s) + 3 Cl2 (g) à 2Al Cl3 (s)

Aluminium on heating with hydrogen forms aluminium hydride.

2 Al (s) + 3 H2 (g) à 2 Al H3 (s)

Reaction with Acids and Alkalies

Aluminium is amphoteric. It dissolves in both acids as well as bases with the liberation of hydrogen gas. Aluminium reacts slowly with weakened acid and more quickly with concentrated hydrochloric acid to release hydrogen.

2 Al (s) + 6 HCl (aq) à 2 Al Cl3 (aq) + 3 H2 (g)

Aluminium does not react with dilute sulphuric acid. However, it is oxidized by hot concentrated sulphuric acid to liberate sulphur dioxide gas.

2 Al (s) + 6 H2 SO4 (aq) à Al2 (SO4)3 (aq) + 6 H2O (l) + 3 SO2 (g)

Aluminium does not react with nitric acid at any type of concentration, most likely due to the development of a protective layer of aluminium oxide. The acid is said to render the aluminium passive.

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Nitric acid is, therefore, frequently delivered in aluminium containers. Aluminium dissolves in both sodium as well as potassium hydroxides to develop a soluble aluminate, with the formation of hydrogen.

2 Al (s) + 2 Na OH (aq) + 6 H2O (l) à 2 Na Al (OH)4 (aq) + 3 H2 (g)


Frequently Asked Questions (FAQs):

  1. How does aluminium’s reactivity compare to other metals?
    • Aluminium is highly reactive, readily forming a protective layer of aluminium oxide on its surface, providing excellent corrosion resistance.
  2. Why is aluminium considered corrosion-free?
    • Aluminium forms a thin layer of aluminium oxide when exposed to air, preventing further oxidation, thus making it resistant to corrosion.
  3. What are some practical applications of aluminium’s reaction with air?
    • Aluminium’s reaction with air, forming aluminium oxide and aluminium nitride, is utilized in flashlight photography and in removing air bubbles from molten metals.
  4. How does aluminium react with non-metals?
    • Aluminium readily reacts with halogens, sulphur, nitrogen, phosphorus, and carbon, often accompanied by the release of heat.
  5. What is the significance of aluminium’s reaction with acids and alkalis?
    • Aluminium exhibits amphoteric behavior, dissolving in both acids and bases to liberate hydrogen gas. This property finds applications in various chemical processes.
  6. Does aluminium react with all types of acids?
    • Aluminium reacts slowly with diluted acids but more rapidly with concentrated hydrochloric acid. However, it does not react with dilute sulphuric acid.
  7. Why is nitric acid often stored in aluminium containers?
    • Nitric acid does not react with aluminium due to the formation of a protective layer of aluminium oxide, rendering the aluminium passive.
  8. What happens when aluminium reacts with sodium hydroxide?
    • Aluminium dissolves in sodium hydroxide, forming a soluble aluminate and releasing hydrogen gas.
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