Question

Give reasons :
(i) Conc. $HN{O}_3$ can be transported in aluminium container.
(ii) A mixture of dilute NaOH and aluminium pieces is used to open drain.
(iii) Graphite is used as lubricant.
(iv) Diamond is used as an abrasive.
(v) Aluminium alloys are used to make aircraft body.
(vi) Aluminium utensils should not be kept in water overnight.
(vii) Aluminium wire is used to make transmission cables.

Answer 1

(i) Conc. $HN{O}_3$ can be transported in an aluminum container because the reaction between Al and nitric acid forms a thin layer of oxide on the aluminum surface which makes it passive.

(ii) A mixture of dilute NaOH and aluminium pieces is used to open drain as they react to produce hydrogen gas whose pressure is used to open blocked drains.

$2Al+2NaOH+6H_{2}O\to 2N{a}^{+}\left[Al\right(OH{)}_4{]}^{-}+3H_2$

(iii) Graphite is soft and slippery as it has a layered structure in which different layers are bonded to each other by weak Van der Waals forces and can slide over each other.
Hence, it is used as a lubricant.

(iv) Diamond is used as an abrasive and for cutting tools as it is the hardest substance known.
The carbon atom in a diamond is $s{p}^3$ hybridized and forms strong covalent bonds with 4 other carbon atoms. This forms a rigid 3D structure. It is very difficult to break this structure.

(v) Aluminium alloys are used to make aircraft body as these are malleable and ductile, have high tensile strength and are light in weight.

(vi) Aluminium utensils should not be kept in water overnight. The oxygen present in water reacts with aluminium to form a thin layer of oxide. this oxide may dissolve in water to produce harmful aluminium ions.

(vii) Aluminum wire is used to make transmission cables as aluminium is very ductile material.