Conc.HNO3 can be transported in aluminium containers.Explain why?

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Conc.HNO3 can be transported in aluminium containers.Explain why?

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Answer 1 · 2016-10-01T05:13:39

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The position of Al in the Elechtro-chemical series shows that Al is stronger reducing agent than Hydrogen. When Al metal is added to dilute $H N O_{3}$ $HNO_3$ containing higher concentration of $H^{+}$ $H^+$ ions, it reduces the $H^{+}$ $H^+$ ions in the solution to hydrogen gas and itself gets oxidized to $A l {(N O_{3})}_{3}$ $Al(NO_3)_3$

$2 A l (s) + 6 H N O_{3} (d i l) \to 2 A l {(N O_{3})}_{3} + 3 H_{2} ↑ ⏐$ $2Al(s) + 6 HNO_3(dil)->2Al(NO_3)_3 +3H_2uparrow$

But when Al is dipped in conc . $H N O_{3}$ $HNO_3$ where the concentration of $H^{+}$ $H^+$ ions is very low, it reduces Nitrogen of $H + 5 N O_{3}$ $Hstackrel(+5)NO_3$ molecule to $N O_{2}$ $NO_2$ and itself gets oxidized to $A l_{2} O_{3}$ $Al_2O_3$ which forms very thin invisible protective layer on the metal. It then resists further oxidation of Al atom below the protective layer of $A l_{2} O_{3}$ $Al_2O_3$ .

This occurs when concentrated $H N O_{3}$ $HNO_3$ is kept in Aluminium container and makes transportation of conc. $H N O_{3}$ $HNO_3$ in Aluminium container possible.

The equation of possible oxidation reaction occurred during formation of the protective layer of $A l_{2} O_{3}$ $Al_2O_3$

$2 A l (s) + 6 H N O_{3} (c o n c) \to A l_{2} O_{3} (s) + 6 N O_{2} (g) + 3 H_{2} O (l)$ $2Al(s) + 6 HNO_3(conc)->Al_2O_3(s)+6NO_2(g)+3H_2O(l)$

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Conc.HNO3 can be transported in aluminium containers.Explain why?

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