Question

Which of the statements about aluminium is not correct?
(A) It liberates hydrogen from acid as well as alkalies.
(B) It liberates hydrogen from acid but not from alkalies.
(C) It liberates hydrogen from hot alkali solution.
(D) It liberates hydrogen from boiling water.

Answer 1

Hint: Aluminium is an electropositive metal. It is an amphoteric metal. Amphoteric metals are metals which give reaction with acids as well as bases/alkali.

Step-by-Step Solution:
Aluminium has following properties-
It has low-density and high thermal conductivity.
It is non-toxic.
It has excellent corrosion resistance.
It is the second most malleable metal so it can be easily cast, machined and formed.
It is highly ductile.
It is non-magnetic and does not produce spark when struck.
It reacts with acids to form aluminium chloride and hydrogen is liberated in the process.The reaction is as follows.
$2Al + 6HCl \to 2AlC{l_3} + 3{H_2}$
It reacts with alkalis to form aluminates as the electronegativity of oxygen and aluminium is comparable which makes it possible for aluminium to form covalent bonds with oxygen. Hydrogen is liberated in the process. The reaction is as follows-
$2Al + 2NaOH + {H_2}O \to 2NaAl{O_2} + 3{H_2}$
In reaction with caustic soda, aluminium produces sodium aluminate.
Hence option B is incorrect.

Answer- the answer is B.

Note: Aluminium is used in-
- In electrical transmission lines as it is a good conductor of electricity.
- It forms a highly reflective coating surface for heat and light hence used in coating telescopic mirrors, decorative papers, packages and toys.
- It is used to form alloys which are lightweight and strong.
- It is used in kitchen utensils, window frames, foils and in aeroplane parts.