Which alloy of aluminium is used in air-craft industry ?

Explanation

(a) Boron is a symmetrical solid with icosahedral sahpe. There are `20` faces (equilateral triangle). The faces meet as `12` corners. Each icosahedran consists of `12` boron aroms, `6` of them are bonded by a three-conre two-electron `(3c, 2e)` bond `(2.02 Å)` in separated icosahedra.
(b) An alloy of aluminium which is used in air-craft industry is duralumin. Its composition is `95 % Al, 4 % Cu, 0.5 % Mn` and `0.5 % Mg`.
( c) Finely powdered aluminium, when suddenly exposed to air, reacts vigorosly with aerial oxygen, `O_(2)`. The reaction is highly exothermic and therefore `Al` catches fire.
`4Al_((s)) + 3O_(2(g)) rarr 2Al_(2) O_(3(s)) Delta H = -310 kJ mol^-1`
(d) `2BBr_(3(g)) + 3H_(2(g)) rarr 2B_((s)) + 6HBr_((g))`.