Question

Which of the following is a chemical property of aluminium?
A.It corrodes with air
B.It is soft and malleable
C.It melts at $660{\,^0}\,{\text{C}}$
D.Its density is $2.7\,{\text{gm}}\,{\text{c}}{{\text{m}}^{{\text{ - 1}}}}$

Answer 1

Aluminium is an element of the boron group in periodic table, with symbol Al and having an atomic number -3. Aluminium occurs in abundance on the earth surface. Various forms of aluminium are available such as oxides , sulphates , silicates phosphates etc.. Aluminium is the third most abundant element and the most abundant metal in the earth crust.

Complete step by step answer:
Aluminium is found in many rock minerals and is usually combined with silicon and oxygen , such compounds are called aluminosilicates. Also pure metallic aluminium can be economically produced only from aluminium oxide ore.
Now we look at main advantages of aluminium, that are aluminium has a slim profile and it is a durable metal.it has low maintenance value, anti- corrosive , light metal but strong and flexible , water and air resistant and also it doesn’t strikes spark nor get brittle under extreme cold or heat condition.
Now we can list out main properties of aluminium
-Aluminium is consider as a very good conductor of heat and electricity
-It is silvery white metal with a bluish tinge.
-It is a non- magnetic substance
-It is highly resistant to corrosion
-It is lightweight malleable and very soft
-It possess great tensile strength
Aluminium and its alloys have relatively low density. That is $2.7\,{\text{gm}}\,{\text{c}}{{\text{m}}^{{\text{ - 1}}}}$
Melting point of aluminium is found to be $660{\,^0}\,{\text{C}}$. It is because more energy is needed to break the strong ionic bonds that exist in aluminium.
In the above given properties, the high resistance to corrosion behaviour of aluminium is due to a chemical reaction which occurs in the surface of aluminium when it comes in contact with air. When the surface of aluminium metal is exposed to air, a protective oxide layer forms almost instantaneously. This oxide layer is corrosion resistant.
$4\,{\text{Al }}\left( {\text{s}} \right)\, + \,3\,{{\text{O}}_2}\left( {\text{g}} \right)\, \to \,2\,{\text{Al}}{\,_2}{{\text{O}}_3}\,\left( {\text{s}} \right)$
Here aluminium reacts with oxygen to form aluminium oxide in a redox reaction. The aluminium oxide is tough and does not flake off easily as iron oxide rust does. When rust flakes fall off a surface , additional metal is exposed to air and becomes corroded. The behaviour of Aluminium corrodes with air is a chemical property of aluminium.

Hence option A is correct.

Note:
Aluminium cannot be used in such areas where heavy loads are required, it is because of its ductile nature. Aluminium does not bend as much as steel also it does not absorb vibrations as good as steel .Because of the non- corrosive and non - toxic behaviour it is used for both indoor and outdoor applications.