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Give reasons : (i) Conc. HNO_(3) can be transported in aluminium container. (ii) A mixtureof 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. |
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Answer» Solution :(i) Al reacts with conc.`HNO_(3)` to form a very thin film of aluminium oxideon its surfacewhich protects it from furtheraction. `2Al (s) + 6 HNO_(3) (conc.) rarr underset("Alumina")(Al_(2)O_(3)(s)) + 6NO_(2) (g) + 3H_(2)O (l)` thus,Al becomes passive and hence aluminium containerscan be used to transportconc. `HNO_(3)` . (ii) `NaOH`reacts with Al to evolvedihydrogen gas. The pressure of the gas thusproduced can be used to OPEN cloggeddrains . `2Al(s) + 2NaOH (aq) + 2H_(2)O(l) rarr 2NaAlO_(2) (aq) + 3H_(2)(g)` (iii) Graphite has layered structure in which thedifferent layers are held together by WEAK can der Waaks forcesand hence can be madeto slipover one another. Therefore, graphite acts as a lubricant. (IV) Diamond is very hard and hence can be used as an abrassive. (v) Aluminium alloyssuch as duralumin is light, tough and resistantto corrosion and hence isused to make aircraft body. (vi) Al reactswith `H_(2)O`and dissolved`O_(2)` to form a thi film of alumioniumoxide. `2Al (s) + O_(2) (g) + H_(2)O (l) rarr Al_(2)O_(3)(s) + H_(2) (g)` A very very smallamount of `Al_(2)O_(3)` may dissolve to give a few ppm of `Al^(3+)` ions in the solution. SINCE `Al^(3+)` ions are injurious to health,therefore, drinking water should not be kept in aluminiumutensile overnight. (vii) On weightto weightbasis, aluminium conducts twice as Cu. Therefore, it is used in trasmission cables. |
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